Insert copyright again.

IPython/nbconvert/utils/lexers.py

@@ -24,6 +24,13 b' This includes:'
         to Pygments.
 
 """
+#-----------------------------------------------------------------------------
+# Copyright (c) 2013, the IPython Development Team.
+#
+# Distributed under the terms of the Modified BSD License.
+#
+# The full license is in the file COPYING.txt, distributed with this software.
+#-----------------------------------------------------------------------------
 
 # Standard library
 import re