config/secrets.yml: Rename to config/secrets.yml.example.
For confirmation, use config/secrets.yml instead of config/app_config.yml.
app/controllers/users/*_controller.rb: New. Inhelited devise's.
app/models/*.rb: Make associations.
Arrange views of brands.
app/controllers/brands_controller.rb(#index): Show user's brands only, if user signed in.
Change view and controller to create a new brand (set owner_id automaticaly).
app/views/brands/show.html.erb: Add link to new product.
Arrange view and controllers for new product.
app/views/products/{index,show}.html.erb: Show brand name instead of brand id.
app/controllers/products_controller.rb: Show user's products only, if signed in.