Aisle filter and bug fixes

There were several misunderstandings on my end about the external table
relations. I fixed those and wrote a draft on the aisle filter in
sites_controller.rb. I'm starting to think that the filtering algorythm
may become a pain because it does get quite complicated.
Merge branch 'master' of https://github.com/customato/customato

Conflicts:
	db/schema.rb
	db/seeds.rb