Fix typo news date format with distance_of_time_in_words

When a blog is configured with the distance_of_time_in_words
date_format, the typo news feed on the dashboard crashes because
new_js_distance_of_time_in_words_to_now assumes a Time object that
responds to #utc.  But the _typo_dev.html.erb partial passes a date
object, which does not respond to #utc.

It would make sense to format just the date, but then we'd need to
update the translations to handle the date-only format.  Or perhaps
we'd could call show_dates_as_local_time() on the page, which uses
the browser's locale's date format and makes the server-rendered date
mostly irrelevant.

For now, fix the crash by converting the parameter to_time before
formatting it.

app/helpers/application_helper.rb

@@ -156,6 +156,9 @@ def content_array
   end
 
   def new_js_distance_of_time_in_words_to_now(date)
+    # Ruby Date class doesn't have #utc method, but _typo_dev.html.erb
+    # passes Ruby Date.
+    date = date.to_time
     time = _(date.utc.strftime(_("%%a, %%d %%b %%Y %%H:%%M:%%S GMT", date.utc)))
     timestamp = date.utc.to_i
     content_tag(:span, time, {:class => "typo_date date gmttimestamp-#{timestamp}", :title => time})