Twython

- Removed ``simplejson`` dependency
- Fixed ``destroyDirectMessage``, ``createBlock``, ``destroyBlock`` endpoints in ``twitter_endpoints.py``
- Added ``getProfileBannerSizes`` method to ``twitter_endpoints.py``
- Made oauth_verifier argument required in ``get_authorized_tokens``
- Update ``updateProfileBannerImage`` to use v1.1 endpoint

- Added missing slash to ``getMentionsTimeline`` in ``twitter_endpoints.py``

- Updated ``twitter_endpoints.py`` to better reflect order of API endpoints on the Twitter API v1.1 docs site