GTBlame & GTBlameHunk
Merge branch 'blame' of https://github.com/Uncommon/objective-git into Blame
Document `hunkAtIndex:`
Document `hunkCount`

Also move it to be above `hunkAtIndex:`
Add error parameter to `blameWithFile:` methods.

Also fix a bug where `git_blame_flag_t` was being passed into
`git_blame_file`, instead of `git_blame_options`.
Small style fixes.

- Remove unnecessary space in method declarations.
- Use self instead of directly accessing the ivar.
Add `enumerateHunksUsingBlock:`

As well as a convenience `hunk` property.
Add `hunkAtLineNumber:` method.
Style fix.
Expose the underlying `git_blame` object.
Style Fixes.

- Use self instead of directly accessing the ivar.
- Use @() instead of `initWithUTF8String:`
- If statements on one line.
GTBlameHunk: Properties called ID renamed to OID.
Implement custom equality for GTBlameHunk.
Add `GTBlame` and `GTBlameHunk` files to project header.
Make GTBlame and GTBlameHunk public.
Typo fix.
Test `GTBlame` and `GTBlameHunk`
Clarify documentation of `originalCommitOID`.
Fix `GTBlame` and `GTBlameHunk` visibility for iOS targets.
Expose all of `git_blame_options` as a `NSDictionary`.

- Adds the necessary GTBlameOptions* keys
- Because `git_blame_options.oldest_commit ` takes a `git_oid` instead
of `const git_oid *` as all other libgit2 APIs use; add a
`GTOID+Private` file.