Fix user search ordering when using postgres

This is the error:

ActiveRecord::StatementInvalid:

PG::InvalidColumnReference:
ERROR:  for SELECT DISTINCT, ORDER BY expressions must appear in select list

LINE 1: ..."users"."last_name") ILIKE 'michaels%')) ORDER BY username A...
Merge pull request #88 from karenc/fix-user-search-in-postgres

Fix user search ordering when using postgres