Make some updates to themes show UI and model fixes

@travisvalentine gonna need your eye on this, made some back end updates:
- Validation requiring several more of the attributes for themes including prices, image, etc.
- Was having trouble getting the category_ids to save, so added that to the permit list in themes_controller
- Setup a method in the app controller to redirect to home page unless you are an admin in case we want to start getting the word out there but don't have it compete yet. Didn't activate it though (commented out before fileter)
- Took out the build_price_list method called on @theme in the create/edit form. The price wasn't persisting if you created a theme and then went to edit it.

Weird that we had to add this in addition to the `{ category_id: [] }`, but I don't get strong params.