Alternative Webserver fix

The issues mentioned in #206 can alternatively be solved by sending a `ContentLength` header to the client instead of closing the write stream.

I had someone ask me about all the additional `drop`s and `close`s in this example, and I feel getting rid of them and solving it via appropriate HTTP headers may be less confusing?

Also, fixed some build breaking issues, I can drop the webserver commit if it's unwanted or open a new PR just for the fixes.
I'm not sure why, but the close_write() seems to be actually needed...
Restoring them fixes http.rs for me

    try!(stream.write(response.as_bytes()));
    let _ = stream.close_write();
    Ok(())