Properly send customized TCP/IP packets with payload.

Hurray for stackoverflow!
https://stackoverflow.com/questions/27218989/how-to-use-golang-to-compose-raw-tcp-packet-using-gopacket-and-send-it-via-raw/27224011#27224011

Must use this api to send out raw tcp/ip packets:
http://godoc.org/golang.org/x/net/ipv4