Merge pull request #306 from libgit2/arthur/update-to-latest-libgit2

Update to the latest libgit2 changes.
Update to latest libgit2
Merge pull request #308 from libgit2/adelcambre/bump-libgit2

Update to latest libgit2
Merge branch 'development' of github.com:libgit2/rugged into arthur/collections