Add support for terminal resizing for exec, attach, and run. Note that for Docker, exec sessions
inherit the environment from the primary process, so if the container was created with tty=false,
that means the exec session's TERM variable will default to "dumb". Users can override this by
setting TERM=xterm (or whatever is appropriate) to get the correct "smart" terminal behavior.
Create error, stdin, stdout, stderr streams first, and only start
copying once all the streams have been created. This fixes an issue
where the client immediately starts sending data for stdin before all
the other streams have been created. This ends up blocking the spdy
connection frame handler and causes the entire exec/attach session to
time out.