Change 37signals to basecamp
Use full path to /bin/sh in cx.pow.firewall.plist ProgramArguments.
Merge pull request #444 from mcmorgan/change-37signals-to-basecamp

Change 37signals to basecamp
Merge pull request #458 from futureimperfect/master

Use full path to /bin/sh in cx.pow.firewall.plist ProgramArguments in case PATH is unset
Migrate from ipfw to pf
use unique name for anchor and update uninstall
do not limit rule to single interface

`on lo0` limits pow to local requests, which excluded xip.io domains.
now, `to self` limits it to local interfaces, and even leaves mapping to other interfaces, like vmnet, intact.