bugs:
- encrypt message length in addition to everything else
- what if filename has spaces? assert fails

features:
- tests!
- actual crypto using sodiumoxide (or similar...)
- a "UCP VERSION" intro mesage before "UCP CONNECT"
- make srcpath a list: can send multiple files as long as destination is a directory
- need to do more sophisticated host splitting to handle IPv6 addresses
- progress bar (per-file?)

packaing/meta stuff:
- benchmarking to the-nsa.org
- --version flag
- README
- man page
- cargo package upload
- debian (.deb) packaging stuff
- ufw firewall entry (/etc/ufw/applications.d/ucp)
- bash completion file (/etc/bash_completion.d/ucp)