Add css to frontend
Implement backend

Implement backend functionality including database functionality,
doing DNS checks, and yo'ing users.
Add example config file
Update requirements.txt
Reorganize code, integrate worker

Split up the Flask frontend code and the backend processing (worker)
into separate files. Integrate the worker using multiprocessing.
Update readme
Improve css, minor fixes
Implement input validation

Using regex, validate the username input to be the standard username
characters (a-zA-Z0-9_) and the two domain fields to be either of form
(subdomain.domain.com) or (domain.com). (Fixes #1)
Use logging instead of print

Fixes #4
Merge branch 'develop'