Refactor public_ip/private_ip to take any network
Don't fail if we can't find IP address for a given network
Add --bootstrap-network option; --private-network now just a special case
Only prefer the access_ip if asking for public network
Rename ip_addr -> ip_address in method names
Add note about --bootstrap-network to README.rdoc, use LABEL terminology
Merge pull request #57 from decklin/bootstrap-network

[KNIFE-366] Allow arbitrary bootstrap networks