Speed up travis builds.
Speed up travis builds.

ruby-rcade/RubyGameDev.com,RailsGEnthusiasts/RubyGameDev.com,PowerCodeGirls/RubyGameDev.com,ruby-rcade/RubyGameDev.com,PowerCodeGirls/RubyGameDev.com,ruby-rcade/RubyGameDev.com,PowerCodeGirls/RubyGameDev.com,RailsGEnthusiasts/RubyGameDev.com,RailsGEnthusiasts/RubyGameDev.com