Actually use our tracking middleware

Move our routers to _after_ the tracking, so that the tracking actually happens before the response is sent. Order of middleware matters, kids.
Use GA instead of mixpanel

Tracks 'API Request' events with some useful properties
Asynch event tracking

I'd rather just send it off and move on, it's not like we're doing something different if it doesn't send
Merge pull request #32 from adorableio/ga_tracking

GA Tracking