Relax Ruby requirements to allow gem with newer versions of Ruby
Relax Ruby requirements to allow gem with newer versions of Ruby

* Ruby 2.1.X is no longer supported (https://www.ruby-lang.org/en/news/2017/04/01/support-of-ruby-2-1-has-ended/)

* Allow any Ruby newer than 2.1.0

dobbs/gamera,gamera-team/gamera,gamera-team/gamera,dobbs/gamera