Revert "add mathjax with bower instead"

This reverts commit fc6e51bcebcd081ff53b9cbe48b54b7bf2bc0106.
Revert "add MathJax to default and recompile"

This reverts commit 4d14df080c8b24bbbb4f935fce2d106f2bc9b499.
use MathJax CDN
recompile assets