Handle AJAX page navigations on GitHub.

This way you can start at a repo's root page, click around on commits, and get
the side-by-side UI for all of them, even if the whole page doesn't get
reloaded.

Implemented by watching for the main page container changing via Mutation
Observers.
Allow side-by-side diffs of changes that are just insertions or deletions.
Remove source map reference for jQuery.

Prevents log spam in the Chrome Dev Tools saying it can't be loaded.
Merge pull request #19 from mihaip/master

Handle AJAX page navigations on GitHub.