Improves markup for schedule

- Implements suggested changes by @allolex. I had to add extra markup
(div.time and div.content) to style them as columns.
- Uses time tag, both for times and days. Too bad there is no ranges on
the time tag.
- I think I might still be suffering from divitis, maybe instead of
div.activity's I should use a ul.activities and li's.
Removes whitespacing and unnecessary br!