Key list refresh

Added library and knife methods for refreshing the key list for a vault item based on the saved SOLR search. The knife vault subcommand is called 'refresh.' Also added fairly extensive testing for the new methods in (and in the process made a few updates to) item_spec.rb and item_keys_spec.rb.

My org runs mostly on virtual hosts and hosts are created and terminated at a non-negligible pace. We are also becoming increasingly dependent on encrypted data bags for managing secrets on the instances, but running 'knife vault update' every time a new client node needs its key added is absurd. I had created a cookbook library that monkey-patched some of this functionality into it so the chef servers could refresh the keys automatically. I've yanked that out and merged it into the current 3.0.0_working branch code.

Also migrated all tests to run under rspec 3.0.0.