Merge pull request #100 from isaacdontjelindell/master

Upgrade CodeMirror to 2.37.
convert mulitplechoice to mchoicemf
Begin to refactor assessments

1.  Use sphinx to number all assessments
2.  Add new directive to control the number prefix or set the number (qnum)
3. Move common functionality from the various assessments into a parent class.
Work in progress

Move rendering out of the run method and into visit methods.  Preparing for the body text to be parsed and rendered by sphinx as a real rst node.
Question text is now handled by sphinx for mchoicemf
Move the Fill in the Blank question to the improved node model.  Minor tweaks to look of the questions.
Update all the chapters to use the qnum directive for specifying a prefix and starting number.  Also modified questions with embedded pre tags to now use proper source code directives, since the body of the questions is now parsed by sphinx.
Merge pull request #102 from isaacdontjelindell/readyfor

Add tabbed directive
Merge remote-tracking branch 'upstream/master'
revert Actex behaviour to default minimized
sample chapter with 3-tabbed odd-numbered exercises