Add error handling to WebSocket handleMessage function, resolves #175

[theghostmac]

Changelog:

• I added a getJsonRpcError function in client.go to handle errors for handleMessage
• I renamed all receivers to c (My IDE automatically fixed that, and undo was difficult).

[Davincible]

@gagliardetto right now there's no rpc error handling, would be great to have this. As an example, error that I was running into;

{"jsonrpc":"2.0","error":{"code":-32600,"message":"Batch size too large for calls using account indexes. Limit is 10"}}