docs(server): http_proxy example

[euclidr]

I added a CONNECT tunneling example #1759

[ahmedcharles]

Suggested change

	// then we can eventually upgrade the connection and talk a new protocal.
	// then we can eventually upgrade the connection and talk a new protocol.

[ahmedcharles]

Looks good to me. Very educational.

[euclidr]

@ahmedcharles there have been a lot of change since this example is written. split method of AsyncRead AsyncWrite in tokio-io is temporary removed, which make it hard to implement tunnel.

I found tokio has plan to get split back, see the issue. I will fix this example once the split is back. Or are there better ways to implement tunnel?

#1884

[ahmedcharles]

See: https://github.com/ahmedcharles/hyper/commit/cc37f87d6ebfd5a3db618852fc1788b2c88db515

It's hacky but it works. (Though, h2 doesn't build at the moment, so when I rebased, it failed to build.)

[euclidr]

@ahmedcharles thanks, it works! I changed your code a little, use tokio_tcp to use tokio_net::tcp, the example runs correctly.

[ahmedcharles]

No problem.

[seanmonstar]

Thanks for doing this, and sorry for taking so long, I've rebased and merged this into master manually!