Initial dockerization

* Dockerfile creation for both web and DB servers
* Modified a few paths to accept optional ENV vars so that the app will function inside of a Docker container. Non-Docker operation is not affected.
Make sure `os.environ` has a key before trying to use it.
Merge pull request #54 from juanpaco/dockerize

Initial dockerization
Merge branch 'dev' of https://github.com/BYU-NLP-Lab/topicalguide into colorlegend
added tooltips