Added search_query methods to item and item_keys for storing/retrieving the search_query string
Changed vault create and vault update to save the search_query string if
it's specified on the command-line.

Added -p option to knife vault show which allows you to print extra
vault data.  It accepts arguments of search, admins, clients or all.
Extra data is added into the data printed to the screen, allowing it to
be formatted per chef knife output.
Updated docs to include -p option
Fixed typo in error message in knife vault create
Merge pull request #74 from eklein/print_admin_data

Store search query & print vault admin data