.. so we can now call that instead of doing the conversion
and formatting all over the code !
NOTE: it still needs to be /called/ in the code, that change
will need to be applied everywhere a metric is displayed
to the user.
.. metrics for time in zone
.. summary on ride summary
Still need to add to cache, histograms and allow editing
of custom zones in a sensible manner (currently edited in kph/mph)
