Implement the TransportStream trait for TcpStream
Implement the TransportStream trait for TcpStream

This makes it possible to use the raw `TcpStream` in an HTTP/2
connection. This is valid under the HTTP/2 spec when a clear-text
TCP connection is established (either through a direct connection
given prior knowledge of the server's HTTP/2 capability or through
an HTTP/1.1 upgrade).

gwicke/solicit,jinnjuice/solicit,Galvanization/solicit,tempbottle/solicit,mlalic/solicit,stepancheg/solicit