Adding support for Mathjax for rendering

[DarwinSenior]

Hi, I stumbled across you https://github.com/euclio/vim-markdown-composer And it is an interesting proejct. I started to use markdown for report and sometimes I would like to use mathjax as well. So, I was thinking if you would like to add mathjax as default option?

[euclio]

Awesome, thanks for the PR! Do you mind squashing the commits into one?

[maximbaz]

Looks like this can be closed as obsolete now, since parser has changed and the new parser doesn't support math rendering.

[euclio]

Yes, I'll likely be adding a custom scripts configuration option to allow users to add MathJax rendering on their own.