Solves issues with the CONNECT response being misinterpreted and others

Related to https://github.com/TooTallNate/Java-WebSocket/issues/88

Solves issues that were preventing it from working in Fiddler (and probably any other proxy)

* Now ignores the "Connection Established" response (which is the response to CONNECTION request) which precedes the "Switching Protocol" header when doing a proxy
* Fixed the CONNECT request headers for proxy
* Use LinkedHashMap instead of TreeMap to guarantee order of headers