Add a "Stats" page with useful information about data

[jaryncolbert]

I would like to see a Statistics page where interesting metrics about the locations data can be displayed.

Ideas:

• Overall number of RCers
• Top 3-5 locations and their counts
• Date/batch of first RCer from each continent

I'm open to other ideas, as well!

[jaryncolbert]

@sequentialchaos also had the idea to show visualizations to accompany the stats - maybe a changing heatmap or something. Very cool!