Hot fix for docker command including DNS warning

Just tried Peas on a different machine and found some bugs. Have any of you new stargazers and watchers tried Peas yet? Don't be shy about feeding back!

I won't merge this until it's got some specs. In fact I might even take it as an opportunity to move over to start using the [docker-api](https://github.com/swipely/docker-api) gem, which would have avoided this problem in the first place.