Planetary Hours library for Arduino

This library uses the sun_rise() and sun_set() functions from the avr-libc time.h library to calculate planetary hours.

For more information on planetary hours, check out these resources:

The planets themselves are represented numerically from 0 to 6 based on the Chaldean order, like this:

#define SATURN 0
#define JUPITER 1
#define MARS 2
#define SUN 3
#define VENUS 4
#define MERCURY 5
#define MOON 6