fixed all examples

made onFailure() a required method in the BinanceApiCallback interfac…

…e, when not implemented, it caused a slient failure of the thread

Merge pull request binance-exchange#178 from mironbalcerzak/master

Support for multi-channel subscription on single websocket.

Merge pull request binance-exchange#178 from mironbalcerzak/master

Support for multi-channel subscription on single websocket.