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.
We actually aren't using `--standalone` just yet with rspec-rails. I think the perf boost we may get from this is worth keeping for now. We probably should remove that note and the old bundler lock-in.

I'm not sure the difficulty in actually using a standalone setup file yet with rspec-rails and probably won't get to investigating that for some time.

:+1: