Clean up PBGitHistoryGrapher
Update for latest objective-git and libgit2
Upgrade project settings
Add my latest Objective-Git fixes
Dramatically reduce command-line `git` parsing when loading rev list

Issue #2
Populate PBGitCommit dynamically
Looks like --left-right wasn't used

Exception may be if passed from the command line, but for now it's
just complicating things.
Prototype loading commits without command-line
Load tag refs, too
Redistribute work of loading commits
Add a reference to the libgit2 source to the Xcode project
Continue cleaning up PBGitRevList
Filter out changes to lock files earlier in the file watcher callback chain
The answer to "is the index changed" is easier for bare repositories
Cache commits within the rev list

They're immutable anyway
Use Objective-Git to create tags

Issue #2
Merge branch 'master' into issues/2
Load tag info sheet with Objective-Git

For issue #2
Merge branch 'refs/heads/master' into issues/2

Conflicts:
	Classes/git/PBGitRevList.mm
Use Objective-Git for repo creation

Issue #2