[test fix] A few minor fixes to ensure basic WebSocket tests are working. Better scope tests by supported protocol

[breaking] Temporarily removed pending refactor: middleware & ProxyTable support

[api breaking] Begin refactor to optimize node-http-proxy by managing one instance of HttpProxy per `host:port` location

[api] Expose adapted version of `stack` so it can be used with HttpProxy instances not created by `httpProxy.createServer()`

closes #80
Conflicts:
	lib/node-http-proxy.js

The number of maxSockets has to be set after the agent is created. Setting the property in the constructor does not work.