Upgrade to MathJax-2.7.1

[tewk]

Thanks for creating scribble-math. Updating to MathJax-2.7.1 fixes a lot of issues for me.

[coveralls]

Coverage remained the same at 65.497% when pulling 3de70e4 on tewk:master into 3a29f77 on jsmaniac:master.

[SuzanneSoy]

Hi @tewk ! Thanks a lot for your PR :) .

In order to avoid bloating the scribble-math package with the full MathJax directory, I use a trimmed down version of MathJax. It is generated by the repo at https://github.com/jsmaniac/scribble-mathjax (the branch v2.6-racket-mini-source should be updated, and once merged, it automatically shrinks MathJax by discarding a lot of unnecessary fonts and features, and automatically pushes the result to the v2.6-racket-mini branch).

I updated MathJax on that repo instead of directly updating it here, and will soon push the shrinked version.

Also, before you decide to use scribble-mathjax a lot, do note that there may be some licensing issues. I asked the MathJax team if MathJax's license could in any way taint the scribble documents using it (https://groups.google.com/d/topic/mathjax-users/IVhc756rJIk). Their answer boiled down to "no, but we are not lawyers so you should check with a lawyer". It is therefore that it is not 100% safe to use scribble-mathjax unless you can afford to pay a lawyer. I intend to place a large warning in the documentation about this, but haven't done this yet.

[SuzanneSoy]

Closed via a088aa8. Sorry for not using your PR directly, and thanks for the heads-up concerning the new version of MathJax!