Add an OID property to GTDiffFile.
Minor cleanup
Merge pull request #249 from libgit2/gtdifffile-oid

Add an OID property to GTDiffFile
Convert -(NSString *)message, -(NSString *)name, -(GTObject *)target, and -(NSString *)targetType to properties.
Use git directories URL for equality.
Use git directory here.
Fix diff spec.
Update GTTag properties to use modern objective-c syntax.
Add GTTagSpec and delete GTTagTest.
(The previous commit accidentally made those changes, this just updates the Project Settings)
++libgit2
Merge pull request #251 from libgit2/testrepo-bare

Make testrepo.git really bare.
Make new properties readonly.

(Style fixes as well)
Documentation.
Convert targetType from NSString to GTObjectType.
Make -(NSString *)description use dot-syntax.
Reverse polarities.
Documentation++.
Whitespace—.
More whitespace--.
Hopefully fixes spacing issues.