[phunge]

I actually like Travis quite a lot except for one issue! At work we use docker for builds, and neither tool can build docker images in such a way that the docker layer cache is utilized. For more details: https://github.com/travis-ci/travis-ci/issues/5358, https://circleci.com/docs/docker/#caching-docker-layers, https://github.com/docker/docker/issues/20316.

This makes our CI builds painfully slow. It's not entirely CircleCI or Travis's fault, it's the interaction between them and docker.