Add a required minimum ruby version to gem spec. (#892)
Add a required minimum ruby version to gem spec. (#892)

* Add a required minimum ruby version to gem spec (2.1)
doorkeeper-gem/doorkeeper,EasterAndJay/doorkeeper,nbulaj/doorkeeper,doorkeeper-gem/doorkeeper,outstand/doorkeeper,mavenlink/doorkeeper,mavenlink/doorkeeper,mavenlink/doorkeeper,EasterAndJay/doorkeeper,moneytree/doorkeeper,outstand/doorkeeper,jasl/doorkeeper,nbulaj/doorkeeper,doorkeeper-gem/doorkeeper,jasl/doorkeeper,outstand/doorkeeper,jasl/doorkeeper,moneytree/doorkeeper