Added basic design for search
modified:   app/views/activities/_search_form.html.erb
modified:   app/views/activities/_when_search.html.erb

Moved the SLug into a library
modified:   app/assets/stylesheets/search.scss

new file:   app/assets/images/back-test.jpg
new file:   app/assets/images/nav.jpg
modified:   app/controllers/activities_controller.rb
modified:   app/models/activity.rb
modified:   app/models/category.rb
renamed:    app/models/category.rb -> lib/slug_mapping.rb