First pass at integer binning
Removing an unnecessary variable
Using rounding
Handle NaN crudely
Change format string when we have an integer
Update pdifftests
Updating binning to use ticks, and turn chartable off if we have any nulls
Filtering out non-chartable values
Moving out of utils
Adding semicolon
Merge pull request #175 from hammerlab/integer_bins

Integer bins via rounding