Adding mathoid as tex to MathML and SVG renderer

Uses nodejs to call phantomjs that renders the
tex input using MathJax and returns a json object
that includes both the SVG and the MathML
representation.

The project was forked from
https://github.com/agrbin/svgtex.

Co-Authored-By: Gabriel Wicke <gwicke@wikimedia.org>
Co-Authored-By: Moritz Schubotz <wiki@physikerwelt.de>
Change-Id: Ie5f24006c3aacd8f61f48ca275acd63a418d7529