Remove errant assert(NO) in _sendFrameWithOpcode
use 'normal closure' close code by default, fixes #127

SocketRocket uses the invalid close code -1 as the value in the default close method. In addition to being invalid, it causes issues when communicating with some libraries. See section 11.7 WebSocket Close Code Number Registry in the WebSocket Protocol RFC 6455 for more detail.
Merge branch 'valid-close-code' of https://github.com/pizthewiz/SocketRocket
Merge branch 'master' of https://github.com/reggie-inmotion/SocketRocket

Conflicts:
	SocketRocket/SRWebSocket.m

Up to PR #161 merged