Moved websocket.py code into a class WebSocketServer. WebSockets
server implementations will sub-class and define a handler() method
which is passed the client socket after. Global variable settings have been
changed to be parameters for WebSocketServer when created.

Subclass implementations still have to handle queueing and sending but
the parent class handles everything else (daemonizing, websocket
handshake, encode/decode, etc). It would be better if the parent class
could handle queueing and sending. This adds some buffering and
polling complexity to the parent class but it would be better to do so
at some point. However, the result is still much cleaner as can be
seen in wsecho.py.

Refactored wsproxy.py and wstest.py (formerly ws.py) to use the new
class. Added wsecho.py as a simple echo server.

- rename tests/ws.py to utils/wstest.py and add a symlink from
  tests/wstest.py

- rename tests/ws.html to tests/wstest.html to match utils/wstest.py.

- add utils/wsecho.py

- add tests/wsecho.html which communicates with wsecho.py and simply
  sends periodic messages and shows what is received.