Adds registry adresses for CLK OUT and alarm functionality of the chip. Adds hex values for setting the CLK OUT frequency. Adds method allowing setting the CLK OUT

Hi I made few improvements to your code. The CLK OUT frequency setting was tested with an LED on Raspberry Pi. It’s an open-drain output – which means current flows from the supply voltage into CLK OUT pin.

I made also some code improvements towards the PEP8 convenction.

The other registry addresses - for the alarm functionality were taken from this How-To : http://tronixstuff.com/2013/08/13/tutorial-arduino-and-pcf8563-real-time-clock-ic/