Have travis automatically build the documentation

[KirstieJane]

At the moment we ask contributors to build the sphinx documentation locally before submitting their pull request. What if travis could do that so we didn't need that requirement!? ✨

Here's a gist I found to maybe help out whomever has time (or the expertise) to work on it! https://gist.github.com/brenns10/f48e1021e8befd2221a2

[Islast]

@KirstieJane , can you create a personal access token for the WhitakerLab (instructions)

The scope needs to be push access to public repositories (this means the repo tickbox)

Once you've done this send it to me over signal or something equally secure

[KirstieJane]

Just pushed an encrypted key to the dev branch 🙀 eda72d5