'analytics'
drop `length` from the tour metadata

It's pulled from the MP3.

`sed -i'' '/length:/d' tours/*.md`
Group stops by where they are in the galleries

It's a bit hard to know where the next 'stop' is. A few times I almost
walked through the doorway to the next gallery only to wonder 'was that
all of them in this gallery?'

This is minimal, but maybe it will clue people in.
Smooth transition between stops

- animate the background changing
- ensure the stop is scrolled into view
- if the image is tall and skinny, crop off the bottom