Improve CDN rollover behavior

[pkra]

As per discussion elsewhere, let's go back to cdn.mathjax.org/mathjax/latest only serving MathJax.js which re-routes all other resources to /N.m-latest.

[dpvc]

The issue1036 branch of my fork of MathJax resolves this. Also, it removes the old roll-over from rackspace to the new can address, since that is no longer active.

[dpvc]

==> Merged