limit relish to modern rubies

Author: JonRowe

Gemfile

@@ -11,7 +11,9 @@ gem 'yard', '~> 0.8.7', :require => false
 group :documentation do
   gem 'redcarpet',     '2.3.0'
   gem 'github-markup', '1.0.0'
-  gem 'relish'
+  if RUBY_VERSION > '2.0.0'
+    gem 'relish'
+  end
 end
 
 platforms :jruby do