Use Buildkite and Docker

[KevinGrandon]

• Adds a dockerfile and docker-compose file for reproducible CI containers.
• Adds a buildkite pipeline for running lintes, browser, and node tests in parallel.

Generates a build page that looks like this:

After landing:

• We have a Buildkite organization blessed for open source, uberopensource. In the future these build pages will be open, but for now we need to invite people to that organization.
• Add the Buildkite webhook to this repo.
• Remove travis.

Fixes #8

[KevinGrandon]

!merge

[old-fusion-bot]

Failed to merge PR: Required status check "continuous-integration/travis-ci/pr" is failing.

[KevinGrandon]

!merge