Remove duplicate degrees.
Fixed a bug where if all students were graduated or withdrew, examining the persist flag would throw an error.
Exported diff.month
Initial version of retention2
Added back mondf. Throws warning.
Added retention2 function.
Fixed transfer calculation that should have been != but was ==
Updated ggplot opts to theme.
Merge pull request #1 from jbryer/master

auto-Merge with initial source repo