Support a MCP23017 backend

Hi, I made a few changes to your HD44780 python library:

* Changed tabs into spaces (see here for why: http://www.python.org/dev/peps/pep-0008/#tabs-or-spaces)
* Cleaned up some old directories
* Removed old references to HD47780 - it is known as a HD44780
* Added a new backend: the MCP23017 16-bit I/O buffer
* _examples/interaction.py_ modifed to use the MCP23017 backend
* Bumped version to 1.1.3

Great work, BTW
 
Regards
Richard