Remove usage of float

Applying ron064 idea (https://github.com/pebble-bike/PebbleBike-PebbleWatchFace/issues/8)

Memory usage:
=============
Before
* Total app footprint in RAM:      17130 bytes / ~24kb
* Free RAM available (heap):        7446 bytes

After
* Total app footprint in RAM:      15346 bytes / ~24kb
* Free RAM available (heap):        9230 bytes
Round speed instead of truncate them
Merge branch 'feature_remove_float' into 1.4