Refactoring and minor improvements

This is rather a big patch which is trying to improve the standard of 
this Python module. The main changes are:

- PEP8 compliant code of the main module and all examples
- allowing to set default brightness and speed during the object 
initialization
- improving parameterization of PyGlow methods
- improving the pulse_loop function to provide more predicable speed
- improving documentation in the README.md
- changing the way how to load the module in more standard way
- adding MIT license respecting the license of the original module
- adding pulse_color function
- adding a new example of binary clock (bin_clock.py)