Generalized code review

I looked at all the files and made some random fixes. Model fields have
been standardized to under_scored instead of camelCased variable names.
Some random syntax errors fixed. /app now has a homepage which gives you
handy links you can use to see and test the various problem types.
singleStepProblem also has some of my edX testing stuff. fastsouth is a
bash script which you can run in order to do ALL the South migrations
instantly.