Changed copy import to be explicit in code

IPython/nbconvert/exporters/exporter.py

@@ -393,10 +393,10 b' class Exporter(Configurable):'
             and filters.
         """
         
-        # Do a deepcopy first, 
+        # Do a copy.deepcopy first, 
         # we are never safe enough with what the transformers could do.
-        nbc =  deepcopy(nb)
-        resc = deepcopy(resources)
+        nbc =  copy.deepcopy(nb)
+        resc = copy.deepcopy(resources)
 
         #Run each transformer on the notebook.  Carry the output along
         #to each transformer