Add usage examples

[robo9k]

While the README (e.g. at 3921525) mentions that

q3py is of no use on its own, a separate Python module is needed to implement the required game logic.

one or more usage examples are required.

This means a hello world snippet, possibly using the mentioned but not completed Cython module , needs to be added to the README and manual/documentation.

• hello world

Furthermore possible usages such as the following should be mentioned:

• Interpret or compile the QVM in Python (LLVM etc.)
• Rewrite the whole (game, cgame, ui) logic in Python
  • Integrate this natively with Big Brother Bot