Export ProxyHttpServer
Export ProxyHttpServer

To more easily support something like:
```
HijackConnect(func(req *http.Request, client net.Conn, ctx *goproxy.ProxyCtx) {
  // ...
  remote, err := ctx.Proxy.ConnectDial("tcp", req.URL.Host)
  // ...
})
```
kofj/goproxy,kofj/goproxy,elazarl/goproxy,elazarl/goproxy,elazarl/goproxy,kofj/goproxy