Auto-generate READMEs

[dvcrn]

This idea got sparked by a conversation on slack. It would be ideal if we could just generate READMEs for each layer.

With the changes we made inside the doc-helper branch, we can already generate a list of options and keybindings

So to summarize:

• Keybindings: We can generate
• Options: We can generate as well
• Package list: Should be no problem. Just construct the URL with atom.io/packages/{{package-name}}
• Install instructions is a no brainer

We need to add a description to each layer and a script for re-generating all READMEs

[danpolanco]

Leaving a stray thought... This could also go the other way and auto-generate code based on the README. I'm guessing that it would be significantly harder to implement though.

get-packages, get-keybindings, etc., would then be unnecessary.