better doc printing.

theano/gof/utils.py

@@ -127,7 +127,7 @@ def uniq(seq):
 
 def difference(seq1, seq2):
     """
-    Returns all elements in seq1 which are not in seq2: i.e seq1\seq2
+    Returns all elements in seq1 which are not in seq2: i.e ``seq1\seq2``
     """
     try:
         # try to use O(const * len(seq1)) algo