Don't create a path just by referencing a comment

That could easily lead to many, many empty comment directories.
Test the "stories" and "story" helpers

And a little tidy of the other code
Tests for the navigation helper

It's a pain to test this and how I do it is annoying. Probably there's
some better method, but this works well enough.
Cleanup "navigation" helper with features Posts being objects now have

Which means it works a lot better.
Add some TODO items that I came across that aren't obvious