Fix for modularized controller using overwrite_params

Hey guys,

I realized some people have had problems with nested controllers and the
:overwrite_params call. The way I fixed it is like this:


I would love to see if other people could improve on this, its not the
prettiest thing.

Oh, the problem that overwrite_params originally causes is that it will
make the url into something like /sub/sub/controller/ when modularized
controllers are involved.