[#82] Configure default logging handler

Add a null handler to prevent 'No handlers could be found for logger
"mwclient.*"' warnings. This seems to be good practice for libraries.

mwclient/__init__.py

@@ -26,3 +26,14 @@
 from errors import *
 from client import Site, __ver__
 import ex
+
+# Logging: Add a null handler to avoid "No handler found" warnings.
+import logging
+try:
+    from logging import NullHandler
+except ImportError:
+    class NullHandler(logging.Handler):
+        def emit(self, record):
+            pass
+
+logging.getLogger(__name__).addHandler(NullHandler())