Use SSL Pinning

This is both a security and usability feature. Without this feature, security-sensitive applications that don't wish to trust the system CA store or have otherwise implemented custom SSLContexts may be unable to communicate with sdk.hockeyapp.net. As a bonus, the traffic between your customers (or is it your customers' customers :) ) and you isn't vulnerable to CA impersonation (it happens). 

The price for all this is the need to update the SDK with the pins of your new SSL certificate upon each renewal.

Used moxie's [AndroidPinning](https://github.com/moxie0/AndroidPinning) library.

Cheers! Love your work.