Support PostgreSql table inheritance
I don't know very much about that particular feature, so I can't really say that I have any plans on implementing it. I think I will defer on this one, but if you'd like to discuss making a pull-request let me know.

PostgreSql has cool feature like [Table inheritance](http://www.postgresql.org/docs/9.0/static/ddl-inherit.html). It'd be good to implement this feature using inheritance field in Meta class of model.
