Try out the new beta build environment

`sudo: false` sends the build to the new setup. Faster boot times, less waiting, and better network perf.

Also a little .travis.yml cleanup.
FWIW, we're pinning to and older bundler due to https://github.com/bundler/bundler/issues/3004 which is apparently fixed in https://github.com/bundler/bundler/pull/3039 but, as far as I can tell, hasn't been included in a release yet.