Update Safe.js to filter mathsize and not throw error for \mmlToken attributes that are filtered.
Add filtering of scriptlevel, scriptsizemultiplier, and scriptminsize (as per Fred's examples).
Move adding the Safe extension to after the configuration is complete so that user configuration of the extensions array can't remove it.
Strengthen class and ID patterns so no extra classes are included.  Use a ninimum size multiplier as well.
Merge branch 'safe-patch' into v2.2-beta
Repack and recombine previous commit
Merge branch 'v2.2-beta' of https://github.com/dpvc/MathJax into v2.2-beta