Currently, there is no way to totally reset your stats but you can set a custom time range for which statistics will be calculated, which effectively does the same thing.
To do this:
- Open up the statistics tab
- Select the tab that says 'all time' in the blue box along the top
- Set the desired time range
Delete A Round
You can delete rounds from the playing history to reset all your stats. Go to Playing History > Select a round > View and Edit > Delete Round.