Add timer to send message to phone.

Polls the phone every 60 seconds. We do this to routinely ask
the ISS api for current location. Pebble does not recommend using
setInterval in js to routinely poll. They recommend setting a timer
on the watch.
Integrate pebble watch messaging to poll ISS api.
Merge pull request #8 from hwhelchel/timer_for_api

Timer for api