Fixed issue with " ," rendered instead of ", "
Merge pull request #18 from woudshoo/comma-space-issue

Fixed issue with " ," rendered instead of ", "
*injections* was never set to nil, so kept growing indefinetely
Merge pull request #19 from woudshoo/injections-growth

*injections* was never set to nil, so kept growing indefinitely
Merge pull request #20 from woudshoo/mathjax-improvements

Mathjax improvements
Mathjax plugin cleanups.
Tiny improvement, do not emit text/x-math-config script section if not needed