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.
make it possible to install from custom source

by setting ARCHIVE_URL you can override the source of the archive on install

bump version
use 127.0.0.1 instead of localhost
add httpPort to be passed to pow
Lock Eco to 1.1.0-rc-3
Merge remote-tracking branch 'koenpunt/ipfw-to-pf' into yosemite
Adjust firewall script

* Set net.inet.ip.forwarding=1 per pfctl(1)
* Redirect rule accepts any destination address
Update installation and uninstallation scripts
Pow 0.5.0