Add binding for pcap Send

Uses pcap_sendpacket(pcap_handle, buffer, bufLen) to send arbitrary packets on the connected interface.

This is tested and working in Windows 7 with WinPCap 4.1.3 and on Linux with libpcap 1.1.1-10 (Ubuntu precise)

Instead of returning an integer, we should instead just throw an error using `pcap_geterr()` if there was an error.