Suggestion: expand discussion of routes and Ember dir layout

When I generated the Ember routes, I ended up with routes/sightings.hbs and routes/sightings/index.hbs.

I made a mistake and put the new code into sightings.hbs instead of sightings/index.hbs. And it worked! At least until I got to chapter 23.

Suggest expanding the discussion and explanation of routes and how they correspond to project layout for dummies like me.