hello_node.py: fixed typo in port from 8000 to 9000 (in the comments)

--HG--
branch : sz0ka/hello_nodepy-fixed-typo-in-port-from-800-1376054112366
Merged in sz0ka/hello_nodepy-fixed-typo-in-port-from-800-1376054112366 (pull request #1)

hello_node.py: fixed typo in port from 8000 to 9000 (in the comments)
Added a full complete example of test-driven development with circuits