:bug: First pass at some nit stats

Very simple first pass at some nit stats. This commit:

 * Includes the Chart.js library (MIT Licensed)
 * Creates a new route /:user/nitstats for viewing nit statistics
 * On the above page, displays a line graph of nits picked and received
   over the past 30 days.
Merge pull request #1016 from rsslldnphy/feature/nit-stats

First pass at some nit stats