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]
use ActiveSupport::Concern refector DoorKeeper::Helpers::Filter
can specify doorkeeper bearer name
add skip_doorkeeper_for helper
use uuid generate default doorkeeper bearer id, avoid conflicts
rename doorkeer_for id option to name
private doorkeeper bearer method
change naming rule for dookeeper bearer method
refactor SelectedDoorkeeperFor initializer
formatting code
reimplement skip_doorkeeper_for
update README with skip_doorkeeper_for