Render DTSTAMP

See http://tools.ietf.org/html/rfc5545#section-3.8.7.2
Merge pull request #2 from gpluess/feature/render-timestamp

Render DTSTAMP
Render STATUS

See http://tools.ietf.org/html/rfc5545#section-3.8.1.11
Merge pull request #3 from gpluess/feature/render-status

Adding STATUS to export
removed @todo for adding STATUS support to calendar event in export