Print to stderr in on_error

Apparently the clever hack for logging in on_error was not so clever
after all.  If logging isn't configured, by the logging modules
definition of not configured, which is root logger not having an
Handlers attached, it will call logging.basicConfig().  Which messes up
setups that define handlers for other loggers than the root logger.

Going directly to the root logger rather than using the broken
convenience methods for logger is not an option either, as logger before
Python 3.2 does not have lastResort on the root logger, and prints an
error when invoked without any handlers.

Resolve by printing tracebacks to stderr by default in on_error.

docs/api.rst

@@ -39,7 +39,7 @@ overriding the specific events. For example: ::
 
 
 If an event handler raises an exception, :func:`on_error` will be called
-to handle it, which defaults to log a traceback and ignore the exception.
+to handle it, which defaults to print a traceback and ignore the exception.
 
 .. versionadded:: 0.7.0
     Subclassing to listen to events.
@@ -53,16 +53,10 @@ to handle it, which defaults to log a traceback and ignore the exception.
 .. function:: on_error(event, \*args, \*\*kwargs)
 
     Usually when an event raises an uncaught exception, a traceback is
-    logged and the exception is ignored. If you want to change this
-    behaviour and handle the exception for whatever reason yourself,
-    this event can be overridden. Which, when done, will supress the
-    default logging done.
-
-    .. note::
-
-        The default ``on_error`` handler logs exception to the root logger
-        instead of a logger under the discord namespace.  This is to ensure
-        that exceptions are output somewhere if logging is not configured.
+    printed to stderr and the exception is ignored. If you want to
+    change this behaviour and handle the exception for whatever reason
+    yourself, this event can be overridden. Which, when done, will
+    supress the default action of printing the traceback.
 
     The information of the exception rasied and the exception itself can
     be retreived with a standard call to ``sys.exc_info()``.