Use localized date formats in interpolate_hash

Interpolated strings containing Times or Dates should respect
default formatting options and locale. This also avoids using
Rails' Time#to_s which will throw a deprecation warning if
a :default format is set.

lib/i18n/interpolate/ruby.rb

@@ -43,7 +43,12 @@ def interpolate_hash(string, values)
                     config.missing_interpolation_argument_handler.call(key, values, string)
                   end
           value = value.call(values) if value.respond_to?(:call)
-          $3 ? sprintf("%#{$3}", value) : value
+
+          if value.respond_to?(:strftime)
+            backend.localize(locale, value)
+          else
+            $3 ? sprintf("%#{$3}", value) : value
+          end
         end
       end