Add time zone support

If we're wanting to stay consistent with the ISO 8601 standard for time and date format, we should probably follow the standard for representing the time zone of the form: `2014-10-07T14:45:15Z` for UTC or `2014-10-07T14:45:15Z-0800` for Pacific.

See http://en.wikipedia.org/wiki/ISO_8601#Time_offsets_from_UTC