Add TCP.recv and tcp_recv

[postmodern]

To compliment TCP.send and tcp_send, there should be TCP.recv and TCP::Mixin#tcp_recv methods. These methods should call connect with the host and port arguments, then calls .recv(1024) to read the first chunk of data sent through the connection. This method is similar to TCP.banner and tcp_banner, but it reads the whole packet of data and doesn't stop at the first newline.

data = TCP.recv(host,port)
data = TCP.recv(host,port, length: 4096)

include Network::TCP::Mixin

data = tcp_recv(host,port)
data = tcp_recv(host,port, length: 4096)