EB3 fix
Rounding decimals to 3 places for the graph to render properly
Adding the hint slides for ps-04 problems
Changing the image extension for the hint slides
removing the typo in the images name
problem 2 set 4 bug from document
Hacked together a new leaderboard.  Doesn't affect existing dashboard code.  Can be disposed after experiment is over.
Merge branch 'jonwetzel'
Selecting the tutor section only for leaderboard.
Changed colors in the new leaderboard.
Clarified new colors leaderboard, and changed display to percents of correct responses.
Improved text for new leaderboard.
Fixed a bug where NAN printed.
Adding a string to the cpi leaderboard, as requested by Kurt.
Adding quiz problem 3