Add tcping to retina

**Is your feature request related to a problem? Please describe.**
I want to be able to simulate TCP traffic with a tool instead of running curl in a while loop. Ideally this tool is able to run with a simple command without additional scripting for an undetermined amount of time.

**Describe alternatives you've considered**
curl in a while loop is the current alternative. For tool alternatives I have also looked at nmap, but it only executes a single TCP handshake and it has the downside of being a heavier binary.