Months are large and behind the weeks
Organize outlines by cohort instead of by month

* Add some tests b/c it's so fkn annoying to have to go to the
  browser to see if things work.
* OutlineListHelpers graduates from a module to a class, b/c when
  testing it, the test helper methods and its helper methods were
  overriding each other. It's not quite a presenter, but kinda close.
  I'm happy with this decision, because fuck modules.
Rename helpers/outline_list_helpers.rb -> presenters/outlines_by_cohort
Line up weeks, week number is horizontal next to outlines

Css is stupid, I had to hard-code sizes into here.
If there is a better way, please:
  (a) fix it
  (b) show me what you did
  (c) tell me all your secrets!!!