Fix incorrect date header when in a timezone with +/- 30 mins

Date headers should be like
`Tue, 15 Jan 2013 14:45:11 -0430`
but are like
`Tue, 15 Jan 2013 14:45:16 -0450`

For info on a time zone with a 30 min difference see http://www.timeanddate.com/library/abbreviations/timezones/sa/vet.html

The original bug for including the date header had it correct with dateFormat but neither the `Z` or `ZZ` in moment are quite the same. My proposed fix isn't very elegant but it seems to work.