Add a Signature Histogram

[venku122]

It would be cool to have a graph that shows signatures earned per day. Potentially a week long breakdown that shows when the signatures were earned during the two week period and a daily view that shows the time of day the signatures were earned. This would be useful to see what days the freshmen were on floor and how many of their signatures were last minute.

[sman591]

Chartkick would make this pretty easy to add