Revert "Merge pull request #12 from rnons/cmdline"

This reverts commit a25f8b1f6020ff68413b2541d082b29119b4f808, reversing
changes made to 3d7846179cb4cdf177d9121547d2e981ebb24b00.

I cannot accept this yet, because it would require a dependence on
containers-0.5.2.1.  When I am ready to abandon support for GHC 7.4.2, I will
revert this revert.