Bump objective-git and make nesscery api changes.
Add IDTTreeCreator and IDTTreeWriter classes.
Rewrite IDTCommitViewController using the new system.
Revert "Bump objective-git and make nesscery api changes."

This reverts commit aba46cec0d4265b10c9ad31b3d8909cacd9396e3.

Conflicts:
	Git!/IDTCommitViewController.m
Don't just rely on a nil commit, also give up if an error isn't nil
Merge branch 'master' into refactor-commit

Conflicts:
	Git!.xcodeproj/project.pbxproj
	Git!/IDTCommitViewController.m
Logic Fixes.
Apparently the merge wasn't complete.

Submodules were a terrible idea.
whitespace--
Merge branch 'master' into refactor-commit
Refactor the initial commit method to support adding files.
Add a way to specify the base tree in writeSelectedChanges

This makes the code a little less presumptuous.
Pass a nil block into `updatePathspecs: error: passingTest:`
IDTTreeCreator: Support added files.
Add a IDTTreeCreatorSpec.
Merge branch 'master' into refactor-commit
Make GTRepository+URLRelativeization.m more resilient.
Rewrite the committing system to use the index.

As part of the change:
- Removes IDTTreeWriter as it’s not needed.
- Renames IDTTreeCreator to GTRepository+TreeCreation.
- Update the app and tests.
Merge pull request #12 from PiersonBro/refactor-commit

Add commit support.