Wire connect button with client code
Global variable to hold instance of SinglePageChat
Issue-Id: #9
Added success and failure callbacks to RTCPeerConnection.setLocalDescription() calls.
Added success and failure callbacks to RTCPeerConnection.setRemoteDescription() calls.
Added success and failure callbacks to RTCPeerConnection.addIceCandidate() calls.
Added failure callback to RTCPeerConnection.createAnswer() calls.
Added failure callback to RTCPeerConnection.createOffer() calls.