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.

While a strong argument can be made that these are useful commands, they are not conducive to the patterns endorsed by Berkshelf. We do not want to encourage incorrect use, and rather should champion "The Berkshelf Way".