Add simple histogram.
Merge branch 'histogram' of https://github.com/mdakin/boom into histogram
Merge remote-tracking branch 'upstream/master' into histogram
Address comments.
Merge branch 'histogram' of https://github.com/mdakin/boom into histogram
Sanity checks for n and c.
Minor doc fix.
Merge pull request #4 from mdakin/histogram

Simple Histogram support. Code is a bit sloppy. Merge if you think it is useful.