Hack datepicker to make it work with Turbolinks 5.x

Patch extracted from here the comments on turbolinks issue 253 and
converted to vanilla javascript.

The hide action over datepickers ensures us that opened datepickers
will be closed before leving the page. Previously if you open any
datepicker and then move to previous page you will keep seeing the
datepicker in the restored page.

spec/system/admin/banners_spec.rb

@@ -190,6 +190,34 @@ describe "Admin banners magement" do
     expect(page).to have_field "Post started at", with: "22/02/2002"
   end
 
+  scenario "when date picker is opened and click on browser history back datepicker is closed", :js do
+    banner = create(:banner)
+    visit admin_banners_path(banner)
+    click_link "Edit banner"
+    find_field("Post started at").click
+
+    expect(page).to have_css "#ui-datepicker-div"
+
+    go_back
+
+    expect(page).to have_content("Banners")
+    expect(page).not_to have_css "#ui-datepicker-div"
+  end
+
+  scenario "date picker works after using the browser back button", :js do
+    banner = create(:banner)
+
+    visit edit_admin_banner_path(banner)
+    click_link "Manage banners"
+
+    expect(page).to have_link "Edit banner"
+
+    go_back
+    find_field("Post started at").click
+
+    expect(page).to have_css "#ui-datepicker-div"
+  end
+
   scenario "Delete a banner" do
     create(:banner, title: "Ugly banner",
                     description: "Bad text",