four time fixes

[arichnad]

1. Time zone fixes: we were parsing dates and times without the correct time zone information.
2. A sleep parameter, so we can keep under the strava rate-limiting / throttling. (I think this could be made much smarter, by literally rate-limiting under the strava throttling)
3. When merging json lists, make sure the data is sorted, so we can more easily see the most recent date we have data for.
4. Gpx files had the wrong times in them. (This code isn't perfect either, but it will always show the correct time)

[lorenzobenvenuti]

LGTM

I think this could be made much smarter, by literally rate-limiting under the strava throttling

I think it's fine for now, we can update it later with a more elegant solution