Increase database portability by using AREL

Using AREL to compose a series of matching statements concatenated with
OR allows us to hit the database once, instead of once for each column
we want to match on, and lets AREL determine if we want LIKE or ILIKE.

Changes to be committed:
  modified:   app/controllers/searches_controller.rb
Merge pull request #38 from rwalters/master

Increase database portability by using AREL