Feature/multiple photo viewer

Added the ability to add multiple photos to an art piece. Extracted photo from art piece and created a new class. Added nested forms in the add and edit views for art piece. Made it so you can view all the pictures in the show page and one on the index page.
> Or just check to see within the divs on the view page check to see if there
> are no images?

That one. I don't mean context in the rspec sense.