Autodetect ArrayBuffers as binary when sending.

Increase compliance with WebSocket API:
http://www.w3.org/TR/2012/CR-websockets-20120920/#dom-websocket-send

Add the type attribute to MessageEvent:
http://www.w3.org/TR/2012/CR-websockets-20120920/#handler-websocket-
onmessage
check instanceof Buffer for binary data
test auto-detecting buffer as binary
Merge pull request #172 from arlolra/message

Autodetect ArrayBuffers as binary when sending.