Test on Ruby 2.4.
Test on Ruby 2.4.

moneytree/doorkeeper,doorkeeper-gem/doorkeeper,mavenlink/doorkeeper,jasl/doorkeeper,mavenlink/doorkeeper,nbulaj/doorkeeper,outstand/doorkeeper,EasterAndJay/doorkeeper,jasl/doorkeeper,mavenlink/doorkeeper,EasterAndJay/doorkeeper,doorkeeper-gem/doorkeeper,outstand/doorkeeper,doorkeeper-gem/doorkeeper,jasl/doorkeeper,moneytree/doorkeeper,nbulaj/doorkeeper,outstand/doorkeeper