Improved websocket binary support detection

A facke connection to 'wss://localhost:17523' (randomly chosen) to detect
the WebSocket binary support is not the best solution.
First of all, check of prototype has the property 'binaryType'. If not,
perform a dummy connection to 'wss://.' instead of 'wss://localhost:17523'.

This patch was inspired by the discussion and implementation of Modernizr:
https://github.com/Modernizr/Modernizr/issues/370
https://github.com/Modernizr/Modernizr/blob/master/feature-detects/websockets/binary.js