Select the first valid IP if all other checks fail

- If there is no 'public' or 'private' network name, and none has been
  user-configured, just pick the first ip given by server.ip_addresses.
- When the floating_ips extension is forbidden with a 403, treat it the
  same as a 404 when running get_ip
Reduced the complexity of get_ip and create by extracting methods
Drop Ruby 1.9.2
Merge pull request #57 from test-kitchen/roboticcheese/drop-ruby-1.9.2

#56 + drop Ruby 1.9.2