dropping legacy doorkeeper_for and welcome doorkeeper_authorize!
Merge pull request #448 from jasl/new_filter_api

dropping legacy doorkeeper_for and welcome doorkeeper_authorize!
Undo behavior change on specs.

See
https://github.com/doorkeeper-gem/doorkeeper/pull/448/files#diff-403546b64759d2fcb933e8345a827403L2.
Update CHANGELOG. [ci skip]
README notifies that docs may differ per version.

[ci skip]