[CHEF-2984] Change Moneta dependency to Juno.

I am sending a pull request to switch from Moneta to Juno, an actively maintained Moneta replacement. 
This is one of the blockers for packaging Chef for Fedora.

This should solve following issues CHEF-2984 [1] and CHEF-2591 as well and removes the monkey patch for Moneta.

RSpec gave me the same results before and after this change:
```
5733 examples, 0 failures, 48 pending
```

[1] http://tickets.opscode.com/browse/CHEF-2984