allow for List traitlets to come from command line

IPython/utils/traitlets.py

@@ -1208,6 +1208,11 class Container(Instance):
         raise TraitError(e)
 
     def validate(self, obj, value):
+        # Command line arguments come in as strings, let's make them into
+        # lists so we can proceed with validation
+        if isinstance(value, basestring):
+            value = value.split(',')
+
         value = super(Container, self).validate(obj, value)
         if value is None:
             return value