Drop and rename commands

I gave it a few days to think about, but after our conversation this past weekend, I think @ivey is right. 

Let's start a discussion here, but here's my proposal:

1. Remove `berks open`
2. Remove `berks show`
3. Rename `berks info` => `berks show`

We really should not be encouraging users to play in our shelf, and I think those commands go directly against the larger Berkshelf vision. I think, if we really want to enforce the standard that we are developing, these commands are an anti-pattern.