Implement the search API end-point.

Creates GET /api/v1/search&q=COOKBOOK_QUERY. Currently returns the cookbooks
with a similar name. This is not the expected end result, as it should do a full
text search based on the name, maintainer and description of the cookbook.

LeanKit Card: Super-20
https://chef.leankit.com/Boards/View/87539991/90240856
Expand upon Cookbook.search to be more extensive.

Search across the name, maintainer, category and description of Cookbooks.
Add pg_search for Cookbook search.

This removes Cookbook.search in favor of a pg_search_scope across multiple
attributes on cookbooks.