Corrected blank case, empty array, array of nil, of blank

Added a custom method on the model to display the time nicely
modified:   app/helpers/query_helper.rb
modified:   app/models/activity.rb
modified:   app/views/activities/show.html.erb
Added format to display date nicely
modified:   app/models/activity.rb
modified:   app/views/activities/show.html.erb

Added stronger font-weight for And Or on the front page
modified:   app/assets/stylesheets/search.scss
Fixed exception if no date
modified:   app/models/activity.rb
modified:   app/views/activities/results.html.erb