Utilize have_css to let capybara wait

Utilize the built in capybara checks to allow the page to wait until fully loaded.
This should fix #485

spec/system/user_show_spec.rb

@@ -8,10 +8,9 @@
 
     it "renders the proper date value for sorting by last edited", js: true do
       work_last_edited = work.updated_at.strftime("%Y-%m-%d %H:%M:%S %Z")
-      sort_value = '<td class="last-edited" data-sort="' + work_last_edited + '">'
       sign_in user_admin
       visit user_path(user_admin)
-      expect(page.html.include?(sort_value)).to be true
+      expect(page).to have_css('td.last-edited[data-sort="' + work_last_edited + '"]')
     end
 
     it "renders the collection names as links", js: true do