Add spec to show how to use rank in WHERE clause
Add spec to show how to use rank in WHERE clause

[#23]
undergroundwebdesigns/pg_search,savef/pg_search,rigoleto/pg_search,undergroundwebdesigns/pg_search,mpivaa/pg_search,savef/pg_search,paultyng/pg_search,rigoleto/pg_search,Casecommons/pg_search,paultyng/pg_search,mpivaa/pg_search,Casecommons/pg_search