docs: Added TROUBLESHOOTING.md

TROUBLESHOOTING.md

@@ -1,11 +1,60 @@
+If you have a non-library SendGrid issue, please contact our [support team](https://support.sendgrid.com).
+
+If you can't find a solution below, please open an [issue](https://github.com/sendgrid/sendgrid-nodejs/issues).
+
+
 ## Table of Contents
-* [Viewing Mail Header](#mail-header)
 
-<a name="mail-header"></a>
-## Viewing Mail Header
+* [Versions](#versions)
+* [Using the Package Manager](#package-manager)
+* [Viewing the Request Body](#stmpapi-header)
+
+<a name="versions"></a>
+## Versions
+
+We follow the MAJOR.MINOR.PATCH versioning scheme as described by [SemVer.org](http://semver.org). Therefore, we recommend that you always pin (or vendor) the particular version you are working with to your code and never auto-update to the latest version. Especially when there is a MAJOR point release, since that is guaranteed to be a breaking change. Changes are documented in the [CHANGELOG](https://github.com/sendgrid/smtpapi-nodejs/blob/master/CHANGELOG.md) section.
+
+<a name="package-manager"></a>
+## Using the Package Manager
+
+We upload this library to [npm](https://www.npmjs.com/package/sendgrid) whenever we make a release. This allows you to use [npm](https://www.npmjs.com) for easy installation.
+
+In most cases we recommend you download the latest version of the library, but if you need a different version, please use:
+
+`npm install @sendgrid/[package name]@X.X.X`
+
+Please check [here](https://www.npmjs.com/org/sendgrid) for a list of package names.
+
+If you are using a `package.json` file:
+
+```json
+{
+  ...
+  "dependencies": {
+    ...
+    "@sendgrid/[package name]": "X.X.X"
+  }
+}
+```
+
+<a name="stmpapi-header"></a>
+## Outputting the STMPAPI Header
+
+You can output the header by the following:
+
+```javascript
+  var header = new smtpapi();
+  ...
+  console.log(header.jsonString());
+```
 
-When debugging or testing, it may be useful to examine pending header to be sent.
+or use it in your options for the transport (Nodemailer example):
 
-```js
-console.log(header.get())
+```javascript
+  var headers = { 'x-smtpapi': header.jsonString() };
+  ...
+  var mailOptions = {
+    ...
+    headers:  headers
+  }
 ```