We can now subscribe within a renderer function.

This saves us having to wrap the components on a on let/fn and makes
things less nested. It's been the case since re-frame 0.9, but I hadn't
gotten around to changing my components.

See:

https://lambdaisland.com/blog/11-02-2017-re-frame-form-1-subscriptions

day8/re-frame#218

Also:

- Moved the reminder load to the `:state-ui-section` handler, which is
  much cleaner. Shouldn't have unnecessary side effects on render.
- Refactored a few functions/components for readability.