nut 2.7.2 (new formula)

nut, also known as network UPS tools, is a set of tools for
communicating with UPSes, PDUs and solar power controllers. It provides
a daemon, logging and drivers. It communicated over serial lines, USB,
SNMP, IPMI and via HTTP. The name 'nut' is not particularly descriptive
and does not help users find UPS tools, but it matches the Debian
package nomenclature.

This pull request requires the 'powerline' new formula pull request.
Many modern UPSs (especially home ones) do not have serial (RS232) connections. Given that, some users may not want serial drivers. I don't in my setup here, for instance.