Add enqueue feature and other updates

This release includes the official addition of the enqueue feature! Now you can type docker-builder enqueue from the top level of your repo and automatically enqueue a build on your build server.

Other updates include:

• allow enqueue and init commands to work with git remotes starting with git://, http://, https://, & git@ and also those not ending with .git
• optimizing the Dockerfile to make the image ~130mb smaller
• using an external fmtpolice script (from https://github.com/rafecolton/fmtpolice) instead of copying/pasting the logic everywhere
• updating vauth version (parsing GitHub and TravisCI webhooks is now a little faster)
• use sudo: false on Travis for faster builds
• make all tests work with go test ./... (and no longer run tests with ginkgo)
• add code coverage stats using coveralls