Store search query & print vault admin data

This is a first stab at doing two things:

1. Storing the search query when you update or create a vault and specify a search string on the command-line

2. Allow for printing of the search query, clients, or admins via a command-line option.

To print the extra data, pass -p or --print to knife vault show <vault> <item> with one of the following arguments:

search
clients
admins
all

I didn't update docs yet because this is a first attempt.  Let me know what you think :)

This fixes issue #66.