for discussion in http://stackoverflow.com/questions/22106169/how-does-one-query-a-postgres-array-using-the-gin-index

gistfile1.txt

app_development=# select * from things;
 id |     tags      
----+---------------
  1 | {blue,yellow}
  1 | {blue,red}
  1 | {yellow,red}
  1 | {blue}
(4 rows)

app_development=# select * from things where tags <@ '{"blue"}';
 id |  tags  
----+--------
  1 | {blue}
(1 row)