Add example for SelectFunc
Add example for SelectFunc

fixes #6

rsto/pgx,plopik/pgx,plopik/pgx,jackc/pgx,jackc/pgx,axsy-dev/tern,jackc/pgx,deoxxa/pgx,jackc/tern-deb,jackc/pgx,jackc/tern,silviucm/pgx,kelvich/pgx,silviucm/pgx,jonasi/pgx,josephglanville/pgx,silviucm/pgx,plopik/pgx