Added an example for postgresql array type custom field in model docs 
Dang, does that "just work" ?
 So you are missing code to register the field with the database class -- db_field should be "textarray" and then you register the type "textarray" with "Text[]".

I tested this myself and got it working, but because peewee doesn't support (yet) any interesting array operations, I am not going to include this example for now as it might lead people to believe that peewee supports PG array operations.
 Cheers for the tip. Yeah was pretty neat it just worked. 
Looking forward to the updates. 

Thought this might help in the docs.
