[render_math] tests for render_math

[danmackinlay]

As per #693 we need tests for render_math so that we know whether #693 broke it or not

[danmackinlay]

There are a few forks of the plugin around now;
As I said i #693, I think that based on the current projections, the chance of me writing tests for render_math in any finite time are low, as it is at this point are low down a very long TODO list full of things for my day-job. I am shamefully using my own fork rather than contributing back to the main tree like a responsible person. See https://github.com/danmackinlay/pelican-plugins/tree/master/render_math

Do any of the current active render_math contributors have interest for this, or should we close it?
@jerryasher, @barrysteyn, @justinmayer, @drorata, @Mirzal...

[drorata]

I'm afraid I won't have the time to contribute/provide the tests. That's a shame; I know.

[kdeldycke]

FTR, render_math plugin has been moved to its own repository at: https://github.com/pelican-plugins/render-math