Remove misspelled (and unneeded?) `bundle_args`
Sort Travis CI config keys lexicographically
Route Travis CI build to container-based infrastructure

See
<http://docs.travis-ci.com/user/workers/container-based-infrastructure/#Routing-your-build-to-container-based-infrastructure>.
Make Travis CI build the master branch
Try building MAGE on Ruby 2.1.5
Remove Ruby version dependent gem ruby-debug19
Merge pull request #129 from datasektionen/vk-travis-yml

Misc. .travis.yml fixes