Changed comment.

theano/sandbox/rng_mrg.py

@@ -652,7 +652,7 @@ class MRG_RandomStreams(object):
 
         """
         # A list of pairs of the form (input_r, output_r), representing the
-        # update rules of all the random states generated by this RandomStreams"""
+        # update rules of all the random states generated by this RandomStreams.
         self.state_updates = []
 
         super(MRG_RandomStreams, self).__init__()