Feature/error handling

-  simplies a little error handling in webRTC/Wallet/controllers. Still needs some refactoring, as 
suggested in https://github.com/bitpay/copay/issues/433
- handles more error messages
- removes turn servers in config, until we provide a known source. 
- Cleans up the stun server list. 
- updates to peerJS 0.3.8, and use its bower bundle.