Requires CL 5285044

client.go:
* add Dial, ClientConn, ClientChan, ClientConfig and Cmd.

doc.go:
* add Client documentation.

server.go:
* adjust for readVersion change.

transport.go:
* return an os.Error not a bool from readVersion.

R=rsc, agl, n13m3y3r
CC=golang-dev
https://golang.org/cl/5162047