minor json fixes that caused the docker server to return 500s
Added requirements file
Fixed a bug where images and containers would be removed after a successful build
Trim whitespace in dockerfile command args
Bumped version
Merge pull request #2 from cove/master

Minor type fixes that caused the docker server to return 500s
Improved error reporting (thanks @johncosta) and don't encapsulate ports in a list in container_config
Fixed 'cmd' command in builder. container config now accepts command as a string or a list and converts accordingly.
Bumped version to 0.0.4