* Moved "Before Submitting a Pull Request" to the top
* Removed discussion of the standard Github PR workflow
(Contributors who don't know how to create PRs on Github at all can find
that information elsewhere. For the rest, it's just noise.)
* Misc copy edits
This is mainly intended to support jasmine-browser-runner, which will load
a script that configures the env in between the two boot files (boot0.js and
boot1.js). The single-file boot.js is retained for now but will be removed
in a future release.
The old contributing docs had a misaligned nested unordered-list, which
resulted in it creating a new list instead of being nested under its
parent.
It also seems like it would be useful to have the "revert your changes"
prose as part of the "Before Committing" section, since otherwise people
may miss it and have to amend.
