Github improved

Adds in-page changeset unfolding, and some other niceties for github's Commit History view.

This extension changes how you interact with github, letting you do more directly from the Commit History view, where all the interesting stuff happens, and without leaving the page. Key feature: Click anywhere in a commit that isn't already a link to unfold that commit's diff, and any part of the commit message github truncated. Clicking the commit header again folds it back again, and you can fold and unfold the individual file diffs in the unfolded version by clicking their title bars. This add-on is MIT licensed, and you are encouraged to fork it and to hack on ideas and features you miss yourself. My main goal with the add-on is to show how these features are too useful to do without, so github adopts them for everybody visiting the site, with or without this add-on. From time to time, especially as github changes their views and functionality, it is a good bet parts or all of this add-on may be defunct, but as long as features remain in frequent use and appreciation, maintenance will eventually catch up.