Support nested models

[darinwilson]

You currently have to jump through a few extra hoops if you want to have torch forms for e.g. a model on the other side of a has_many relationship. I'm not sure how practical this would be, but I wonder if it would be possible to do something like:

mix torch.gen eex Admin Post:Comment comments body:text inserted_at:date

and have it do the right thing(s).