Fixes #97. Added a method kwarg to the fetch_token endpoint to allow for facebook's GET requests for app tokens.
Made the method code a bit better. Added to docstring for fetch_token method. Raise ValueError if not GET or POST.
Merged with upstream updates.
Merge pull request #98 from nicksloan/get_tokens

Fixes #97. Added a method kwarg to the fetch_token endpoint to allow for...