use the `gtfs` library from Rubygems

now that I've pushed a new version: https://github.com/nerdEd/gtfs/issues/19
upgrading to Rails 4.1.8

http://weblog.rubyonrails.org/2014/11/17/Rails-3-2-21-4-0-12-and-4-1-8-have-been-released/
updating gems
Merge pull request #22 from transit-land/update-gems

Update gems