Fixed #82. 'enable_attributes' honors 'safe_mode'.

Note that you can still explicitly set 'enable_attributes' and that
value will be honored regardless of 'safe_mode'. However if 'safe_mode'
is on and 'enable_attributes' is not explicitly set, then
'enable_attributes' defaults to False.

markdown/__init__.py

@@ -122,6 +122,10 @@ def __init__(self, *args, **kwargs):
             setattr(self, option, kwargs.get(option, default)) 
 
         self.safeMode = kwargs.get('safe_mode', False)
+        if self.safeMode and not kwargs.has_key('enable_attributes'):
+            # Disable attributes in safeMode when not explicitly set
+            self.enable_attributes = False
+
         self.registeredExtensions = []
         self.docType = ""
         self.stripTopLevelTags = True