Add CI + test suite to RMG-website

[jonwzheng]

Motivation

The RMG website code is fairly large, and changes upstream in RMG-Py and RMG-database have the ability to affect functionality of the website.

Some unit tests are already available - we should set up continuous integration that runs these tests and also checks that the website can build properly.

Implementation

We can follow the examples followed by RMG-Py etc. to get this working.