add pkt2flow

pkt2flow splits a large PCAP file as written by tcpdump or snoop into individual tcp or udp streams, again in PCAP format. These subfiles can then be analyzed individually.

OSX support has been added recently, but not yet released, so this formula references my fork of the original project in order to have a reference release. Once the original project incorporates my changes I will update the Formula to point to a https://github.com/yalla/pkt2flow/releases release.