GitLab

It does not make sense to toggle night mode
or start another round of countdown during
calibration.

Closes #4.

* The 'int' return signature and the comment
'Returns the number of remaining leds' sounds like the
function would return its current countdown state.
However, it only returns the number of remaining
leds after the button was released. Thus change
the type to 'bool' and return 'true' after a
successful countdown

* Do not use 1 as return value for night mode,
because it is ambigous. Return 'false' instead.