Update travis-ci config and remove unused bits
Update travis-ci config and remove unused bits

Install gems with bundler on travis and remove all the unused bits of
the configuration.

mysociety/popit,openstate/popit,mysociety/popit,Sinar/popit,mysociety/popit,mysociety/popit,openstate/popit,Sinar/popit,Sinar/popit,openstate/popit,openstate/popit,mysociety/popit,Sinar/popit