Add binding for pcap Send

Updates completed as per your comments on the previous pull request.
I also changed the example to match the change to ThrowException in the send method.

FWIW, my issue with >60 second spool up was in pcap_findalldevs. My system was hanging when iterating through the USB driver for interfaces!  Nothing to do with our code. tcpdump was showing the same behaviour when no interface was specified.
That or make it optional. Default to the length of buffer if the length to send is not provided?