docs: update readme to add wait best practice recommendation that was given by Kent in issue 78. (#79)

Author: RyanAtViceSoftware

.all-contributorsrc

@@ -227,6 +227,15 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "RyanAtViceSoftware",
+      "name": "Ryan Vice",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/10080111?v=4",
+      "profile": "http://www.vicesoftware.com",
+      "contributions": [
+        "doc"
+      ]
     }
   ]
 }

README.md

@@ -16,7 +16,7 @@
 [![downloads][downloads-badge]][npmtrends]
 [![MIT License][license-badge]][license]
 
-[![All Contributors](https://img.shields.io/badge/all_contributors-22-orange.svg?style=flat-square)](#contributors)
+[![All Contributors](https://img.shields.io/badge/all_contributors-23-orange.svg?style=flat-square)](#contributors)
 [![PRs Welcome][prs-badge]][prs]
 [![Code of Conduct][coc-badge]][coc]
 [![Join the community on Spectrum][spectrum-badge]][spectrum]
@@ -374,6 +374,8 @@ The default `interval` is `50ms`. However it will run your callback immediately
 on the next tick of the event loop (in a `setTimeout`) before starting the
 intervals.
 
+> NOTE: `wait`'s callback can be called many times and because of this you should use as few `wait` calls as possible in each test and put minimum amount of code that absolutely needs to be waited on inside each `wait`'s `callback`. This will help your tests run faster and can avoid unnecessary runtime complexity.
+
 ### `waitForElement`
 
 See [dom-testing-library#waitForElement](https://github.com/kentcdodds/dom-testing-library#waitforelement)
@@ -807,7 +809,7 @@ Thanks goes to these people ([emoji key][emojis]):
 | :---: | :---: | :---: | :---: | :---: | :---: | :---: |
 | [<img src="https://avatars1.githubusercontent.com/u/1241511?s=460&v=4" width="100px;"/><br /><sub><b>Anto Aravinth</b></sub>](https://github.com/antoaravinth)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=antoaravinth "Code") [⚠️](https://github.com/kentcdodds/react-testing-library/commits?author=antoaravinth "Tests") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=antoaravinth "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/3462296?v=4" width="100px;"/><br /><sub><b>Jonah Moses</b></sub>](https://github.com/JonahMoses)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=JonahMoses "Documentation") | [<img src="https://avatars1.githubusercontent.com/u/4002543?v=4" width="100px;"/><br /><sub><b>Łukasz Gandecki</b></sub>](http://team.thebrain.pro)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=lgandecki "Code") [⚠️](https://github.com/kentcdodds/react-testing-library/commits?author=lgandecki "Tests") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=lgandecki "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/498274?v=4" width="100px;"/><br /><sub><b>Ivan Babak</b></sub>](https://sompylasar.github.io)<br />[🐛](https://github.com/kentcdodds/react-testing-library/issues?q=author%3Asompylasar "Bug reports") [🤔](#ideas-sompylasar "Ideas, Planning, & Feedback") | [<img src="https://avatars3.githubusercontent.com/u/4439618?v=4" width="100px;"/><br /><sub><b>Jesse Day</b></sub>](https://github.com/jday3)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=jday3 "Code") | [<img src="https://avatars0.githubusercontent.com/u/15199?v=4" width="100px;"/><br /><sub><b>Ernesto García</b></sub>](http://gnapse.github.io)<br />[💬](#question-gnapse "Answering Questions") [💻](https://github.com/kentcdodds/react-testing-library/commits?author=gnapse "Code") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=gnapse "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/2747424?v=4" width="100px;"/><br /><sub><b>Josef Maxx Blake</b></sub>](http://jomaxx.com)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=jomaxx "Code") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=jomaxx "Documentation") [⚠️](https://github.com/kentcdodds/react-testing-library/commits?author=jomaxx "Tests") |
 | [<img src="https://avatars1.githubusercontent.com/u/29602306?v=4" width="100px;"/><br /><sub><b>Michal Baranowski</b></sub>](https://twitter.com/baranovskim)<br />[📝](#blog-mbaranovski "Blogposts") [✅](#tutorial-mbaranovski "Tutorials") | [<img src="https://avatars3.githubusercontent.com/u/13985684?v=4" width="100px;"/><br /><sub><b>Arthur Puthin</b></sub>](https://github.com/aputhin)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=aputhin "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/21194045?v=4" width="100px;"/><br /><sub><b>Thomas Chia</b></sub>](https://github.com/thchia)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=thchia "Code") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=thchia "Documentation") | [<img src="https://avatars3.githubusercontent.com/u/20430611?v=4" width="100px;"/><br /><sub><b>Thiago Galvani</b></sub>](http://ilegra.com/)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=thiagopaiva99 "Documentation") | [<img src="https://avatars1.githubusercontent.com/u/19828824?v=4" width="100px;"/><br /><sub><b>Christian</b></sub>](http://Chriswcs.github.io)<br />[⚠️](https://github.com/kentcdodds/react-testing-library/commits?author=ChrisWcs "Tests") | [<img src="https://avatars3.githubusercontent.com/u/1571667?v=4" width="100px;"/><br /><sub><b>Alex Krolick</b></sub>](https://alexkrolick.com)<br />[💬](#question-alexkrolick "Answering Questions") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=alexkrolick "Documentation") [💡](#example-alexkrolick "Examples") [🤔](#ideas-alexkrolick "Ideas, Planning, & Feedback") | [<img src="https://avatars3.githubusercontent.com/u/1239401?v=4" width="100px;"/><br /><sub><b>Johann Hubert Sonntagbauer</b></sub>](https://github.com/johann-sonntagbauer)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=johann-sonntagbauer "Code") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=johann-sonntagbauer "Documentation") [⚠️](https://github.com/kentcdodds/react-testing-library/commits?author=johann-sonntagbauer "Tests") |
-| [<img src="https://avatars2.githubusercontent.com/u/2224291?v=4" width="100px;"/><br /><sub><b>Maddi Joyce</b></sub>](http://www.maddijoyce.com)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=maddijoyce "Code") |
+| [<img src="https://avatars2.githubusercontent.com/u/2224291?v=4" width="100px;"/><br /><sub><b>Maddi Joyce</b></sub>](http://www.maddijoyce.com)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=maddijoyce "Code") | [<img src="https://avatars2.githubusercontent.com/u/10080111?v=4" width="100px;"/><br /><sub><b>Ryan Vice</b></sub>](http://www.vicesoftware.com)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=RyanAtViceSoftware "Documentation") |
 
 <!-- ALL-CONTRIBUTORS-LIST:END -->