Convert to CircleCI 2.0

[pjenvey]

The 1.0 style configuration still used in this sample is supposedly retiring this August

https://circleci.com/blog/sunsetting-1-0/

[mostlygeek]

Yes this should be high priority. I'll do it.

[milescrabill]

I made a similar baseline example a few months ago when CircleCI 2.0 was new. See here: https://github.com/mozilla-services/ci-testground.

It uses some extra things like docker caching and circleci workflows, which parallelize the ci build process. You can see an example of the parallelized workflow here.

[mostlygeek]

Closed in #35