Mathjax tests for markdown are messy and complicated, could be improved

[mpacer]

We should be able to make that set of tests much nicer.

For example, the test_markdown2html_math_mixed is dependent on whether there is a space after the final period or not, which is an issue with checking for whether content is "in" the resulting html, and the html paragraph tag closes before a new line if there is such a space.

I don't know a generally good approach to this. Maybe it must be messy but that sort of finicky-ness seems undesirable.

[mpacer]

Note: our current approach to parsing text allows us to treat everything as inline text, which seems bizarre, but – technically – less complicated!

https://github.com/mpacer/nbconvert/tree/mjax_all_inline

I don't know why this is possible. But I think it points toward problems with our current mathjax handling.

[mpacer]

note with #611 all the logic is now inline.

@pxhanus Are you interested in tackling this?

[jzf2101]

@mpacer could we add this to our list of issues for hacktoberfest?

[jzf2101]

@fenwickipedia also could be interesting?