Making html export a cleaner UI experience.
Excluding categories with no assignments and a few optimizations.
Making GhostStudent funcs take null grades.
Other fixes to allow null grades.
Finishing student summary statistics.
Making Ghost Grades more accurate.
Fixing bug where Course w/o optional fields threw NullPointerException.
Some more cleanup on the exported statistics.
Fixing bug where null grades don't error correctly.
Displaying null grades as dashes instead of 0s
Cleaning up chars that the jar didn't like.
Making docs and GUI say the same things.
Merge pull request #90 from spockNinja/finish_exporting

Finish exporting + lots of bug fixes + I'm really tired now...