++expecta and ++specta (also switch to github forks).
Add tests for binary files and crazy diffs.

This is protection against a couple of cases I ran into GHfM. This is
mainly proving the fault is in Mac's code.

Also updated the fixture repo with some nice diffs to test against.
Specifically an image and a minified jquery.
Merge pull request #120 from libgit2/moar-diff-tests

Add more diff tests.
Merge from master.