Add back Hijacking support for http1.1 CONNECT requests.
Reconstruct the schema of the proxied request if it's not filled out.
Add http2 using the go-1.6 net/http built-in support. net/http's http2 doesn't support hijacking, so instead of hijacking the inital CONNECT tcp connection, tunnel proxied requests/responses over the reader and writer streams of the CONNECT request.
fixes redirects