Add github.com/rackspace/gophercloud package as a dependency.

Note this also pulls in:
github.com/kr/text
github.com/mitchellh/mapstructure
github.com/racker/perigee
github.com/tonnerre/golang-pretty
Add a pkg for iptables support

This makes iptables an injectable dependency.  The test for this started off
simple, but got a bit out of hand.  It's starting to become a mocking
framework.
Add v1beta2 API objects
Add a util/exec interface for testing execs.
Fix the exec test, on os x false and true have different paths, but they're in $PATH on all.