Include Ruby version into output of --version.

Helpful for debugging purposes.

Author: nene

lib/jsduck/options.rb

@@ -860,7 +860,7 @@ def create_option_parser
         end
 
         opts.on('--version', "Prints JSDuck version") do
-          puts "JSDuck " + @version
+          puts "JSDuck " + @version + " (Ruby #{RUBY_VERSION})"
           exit
         end
       end