Nicer logic for `platform` var

![Change tactic](http://gifs.gifbin.com/022012/1329246457_train_track_bike_jump.gif)
@ironsidevsquincy 
yep, we already track all 485 of them...

Kill this off, understanding user agents is the job of the analytics software.

![firefox](https://cloud.githubusercontent.com/assets/76709/4063354/f688eee0-2e06-11e4-8d70-e17f0f11932c.png)