Don't use @{..} for XML::RSS{category}

It seems the array returned by split() does not need to be dereferenced
at this stage, but just copied (as is done with the []).

Also, re-order category before pubDate, as was the case prior to
6b87e3d1.

Tested with blogsum-1.1p1 OpenBSD 5.2.

Signed-off-by: Olivier Mehani <shtrom@ssji.net>
Merge pull request #4 from shtrom/master

Issue with category "swallowing" pubDate in RSS2 generation