Implement objectByPeelingTagError: to peel a tag object.
Add objectByPeelingToType:error: to GTObject using git_object_peel.
Change return type to id
Change < to !=
Change return type to id.
Change < to !=
Merge pull request #214 from 5sw/tag_peel

Add wrappers for git_object_peel and git_tag_peel to GTObject/GTTag