Resolves to TODOs in the doorkeeper for helper

Moves token validation from DoorkeeperFor class into the Access Token
class.
Add specs for new methods in AccessToken and Scopes

adds test for includes_scope? acceptable?
Fix a style error in specs
Remove duplicated valid_token? method
Merge pull request #417 from edpaget/fix-todos-in-doorkeeper-for

Fix TODOs in the doorkeeper_for class
allow to contain a query parameter
Merge pull request #432 from znz/allow-query

Please allow to contain a query parameter for hybridauth.
Update CHANGELOG. [ci skip]
No need to specify namespace inside of modules.

* Gets rid of some redundant `self`s.
* Removes an empty method.
Controllers refactors:

* Remove empty methods
* Extracts methods in AuthorizationsController
* Comment adjustment
Failing test for issue 398
Native redirect for implicit token grant bugfix

See: https://github.com/doorkeeper-gem/doorkeeper/issues/398
Moves from update_column to update_attribute

Ensures cross-ORM compatibility.
Removes Revocable module trails
Merge pull request #438 from doorkeeper-gem/issue-398

Native url implicit access token grant redirection bugfix
Update CHANGELOG. README TOC update. [ci skip]