Created a class to generate SupportFlow thread statistics
Created a page to statistics

Currently it shows new/open/closed tickets stats for different time period
as well as different tags
Clicking the number of matching tickets will show them in `All threads`
page
Added type to style tag to maintain backward compatibiliy with old browsers
Add comments to code in statistics page
Merge pull request #136 from VarunAgw/stats

Add a Statistics screen.