Refactoring and minor improvements

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