added translation hooks to timesince and updated message files to reflect them...

added translation hooks to timesince and updated message files to reflect them (and updated the 'de' translation). Additionally some smallish code changes to timesince (that weird zip thingy was just scary - and there is no need to .floor an integer division)


git-svn-id: http://code.djangoproject.com/svn/django/trunk@1359 bcc190cf-cafb-0310-a4f2-bffc1f526a37