Reduce technical debt in how we create Docker releases and versions for LSST the Docs applications.

1. Use setuptools_scm to create semantic versions for the LTD Keeper and Dasher applications based on the repo's Git tag state.
2. Convert Keeper and Dasher to setuptools projects to use setuptools_scm.
3. Create a Makefile to create a Docker image that automatically inserts the version information.
4. Create a Travis CD pipeline that uploads to Docker Hub when a new tag or branch is available.
5. Create an API route that exposes the Keeper API version.