tidy up dependencies
support the button

There's something really weird going on with the button and it's
happening on both my boards so I don't think it's a bad unit. tl;dr: the
button is super unreliable. Sometimes, we don't see the rise unless
there's a double tap. Most of the time, a long press triggers fine. But
then sometimes not.

I'm drawing a blank so I'm committing the code as is. This matches their
sample python code so at least we're all consistent.

And lest you say "surely it's the library", I've verified this behavior
with three go libraries and the python script from Argon. It's a
behavior of the board, not the libraries.
a really dumb demo app for the fan
reorg so that folks can choose which bits they want
guard rails around the fan speed percent
init with working code