Doxygen docs hosted on Github Pages site don't link to Mathjax CDN

[saxbophone]

There's a Cross-Origin-Resource-Sharing issue that prevents the Mathjax library from loading off CDN, which in turn causes maths formulae in the documentation site to not load

(e.g. https://saxbophone.com/arby/v0.4/namespacecom_1_1saxbophone_1_1arby.html#aef0632df77d9ea36228ce5180a2585cd).

Should look like:

Actually looks like:

[saxbophone]

Closed in #101