Improved `Proxy.js` handling of request through another proxy: now it does not assume that any answer from other proxy is OK, and checks for `200 OK`.
Improved `NTLMProxy.js` - now our fake NTLM proxy tries to support authorization on CONNECT requests too.
Updated `test-ntlm.js` for changes in NTLMProxy.
Added test for getting requests through our fake NTLMProxy to `test-proxy.js`. It fails, for now :).