Be faster

- Added profiling in dev (add /?profile=true to any URL)
- Rewrote the unique users time series in SQL to make it faster

Super scientific speed test BEFORE:
![before](https://cloud.githubusercontent.com/assets/2533112/5576296/48aa2962-8fac-11e4-8532-9156e79ef1ce.png)

and AFTER:
![after](https://cloud.githubusercontent.com/assets/2533112/5576297/4b5cb29c-8fac-11e4-8b26-a2a2c82a0cf3.png)