Add copyright statement

apps/circuitpusher/circuitpusher.py

 #! /usr/bin/python
 """
+Copyright 2013, Big Switch Networks, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License"); you may
+not use this file except in compliance with the License. You may obtain
+a copy of the License at
+
+         http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+License for the specific language governing permissions and limitations
+under the License.
+
 circuitpusher utilizes floodlight rest APIs to create a bidirectional circuit, 
 i.e., permanent flow entry, on all switches in route between two devices based 
 on IP addresses with specified priority.