Added documentation and use gitlab-ci templates

This MR adds documentation and uses gitlab-ci templates from the LSC computing CI templates.

The output can be found at https://evan-goetz.docs.ligo.org/pydarm/. Eventually the documentation will be hosted at https://calibration.docs.ligo.org/pydarm/ (though this link currently is not functional)

While the documentation is not fully fleshed out to the fullest extent, it contains a lot of the key features needed for documenting the pyDARM code.

Closes #41 (closed) #89 (closed)