Add status to stacked envs for `rip-envs`

[cldwalker]

Here's the branch: http://github.com/cldwalker/rip/tree/envs
To make stacking envs first class, I could also add a rip-pop to rip-shell if you'd like.
Fyi, 15 tests are failing for ruby 1.8.7.

[cldwalker]

Merged in 5da74f2