Fix search path construction in tests.

This way the tests can be run directly from within the tests directory
and they might also have a chance of running on Windows (where the
path separator is different).

tests/echo.py

@@ -11,8 +11,8 @@ as taken from http://docs.python.org/dev/library/ssl.html#certificates
 '''
 
 import os, sys, select, optparse
-sys.path.insert(0,os.path.dirname(__file__) + "/../websockify")
-from websocket import WebSocketServer
+sys.path.insert(0,os.path.join(os.path.dirname(__file__), ".."))
+from websockify.websocket import WebSocketServer
 
 class WebSocketEcho(WebSocketServer):
     """