improve description of squery in README
improve description of squery in README

KrzysiekJ/epgsql,chef/epgsql,seabirdzh/epgsql,chef/epgsql,shaneutt/epgsql-1,billiob/epgsql,mabrek/epgsql,maximvl/epgsql,talentdeficit/epgsql,kivra/epgsql,chef/epgsql,epgsql/epgsql