fixed deprecated isAlive in thread library

Author: wobrschalek

src/scxml4py/activity.py

@@ -58,7 +58,7 @@ def __init__(self, theId, theEventQueue = None, theData = None):
         self.mThread = None
 
     def start(self):
-        if self.mThread and self.mThread.isAlive():
+        if self.mThread and self.mThread.is_alive():
             logger.debug("Activity <%s> already started"%self)
             return