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.
Fix latest posts date format with distance_of_time_in_words

The Latest Posts on the admin dashboard is showing
"distance_of_time_in_words" as the date of each post, because that
is what is configured as my blog's date format.  Elsewhere, this
date format is treated as a special case rather than a strftime format.

Format the date with display_date_and_time rather than directly calling
strftime on the date and time format of the blog.
Merge pull request #136 from mcary/fix-dashboard-date-format

Fix dashboard date formats