Updates to readme

[probins]

Proposes:

• additional text on module tag
• adding example of using Promise.all for multiple module import (0.17 Promise.all no longer working systemjs/systemjs#498 (comment))
• shuffling a few other bits about for a more logical sequence (IMHO)

Question: why is https://github.com/systemjs/systemjs/blob/master/docs/es6-modules-overview.md in systemjs? This surely belongs here.

[guybedford]

These links do need to be at the top. Perhaps make the first one an anchor link within the README if that's what you're after?

[probins]

These links just repeat what's in the previous section (in a more concise form), and it seemed to me that people coming to this file would want to read the getting started section first, and only then maybe want to move on to more details. So put the documentation links at the end

[guybedford]

The links at the top might be missed, with users wondering where the docs are - nice to make it easy to find on the page.

[guybedford]

Thanks, note that because this repo provides no production workflow, it is not suitable for end-users and is more appropriate for implementors at this point. So the documentation is moving to reflecting that as well somewhat, hence why the basic ES6 module info was removed.

[probins]

if you're moving general usage docs to systemjs, it might be better to have the note on Promise.all in there (somewhere)

[guybedford]

In general, it is advisable to have a single main entry point over multiple import promises, so it's not something I'd want to encourage too heavily.

[guybedford]

Thanks again for the suggestions - it's great to have this documentation feedback.

[probins]

I'm using it for optional loads: parse querystring into an array and load the requested components with Promise.all. I don't think it makes sense in a static situation.