Remove warnings from parse_api_json_response.
OAuth scope-ify all of the things!

* Replaced require_login and require_moderator with restrict_access decorator.

* Specified most of the scopes for functions where require_login and
  require_moderator were previously.

* Added functions to the AuthenticatedReddit class:

  * has_scope
  * is_logged_in
  * is_oauth_session

* Added get_cached_moderated_reddits to the LoggedInRedditor class

* Added additional exceptions to indicate required OAuth states

* Remove NSFWable and relocate functions into Moderatable. As part of this
  change subreddits no longer support `mark_as_nsfw` and `unmark_as_nsfw`. Use
  update_settings instead.

* Added some AccessControlTests. More are needed to test functions when the
  wrong OAuth scopes are used.