ERRORS in Node 4.0+

[morlay]

Since the nodejs merge the iojs, something need to update.
In depedence chains, JSDOM is the big reason to show errors.

Howerver, the current version (0.3.0) of MathJax-node is still with old version (3.1.2),
New changes still work in develop.

There is a unstabled version: https://github.com/morlay/plugin-mathjax
For node 4.0+ user, use mathjax-beta instead, until MathJax-node is ready.

Maybe still a TODO for this plugin :-)