This update add two arguments to voltha when it gets started:
   1) inter-core-subnet: the subnet to connect to for inter core communication
   2) pon-subnet: the subnet to connect to for PON communication

This requires that the voltha_net is created with a specified subnet and that
subnet is specified in the docker compose file, e.g.:

docker network create --driver overlay --subnet 10.0.1.0/24 voltha_net

And in the compose.yml file add the following options:

      - --inter-core-subnet=10.0.1.0/24
      - --pon-subnet=10.0.1.0/24

This update guarantees that the voltha instance is connected to the correct
network.

Change-Id: I5d29ab54282c4ba9aff5ba165fdb37352cfaa0fd
diff --git a/requirements.txt b/requirements.txt
index 7009e4e..bb31099 100755
--- a/requirements.txt
+++ b/requirements.txt
@@ -15,6 +15,7 @@
 jsonpatch>=1.14
 kafka_python>=1.3.1
 klein>=15.3.1
+netaddr>=0.7.18
 networkx>=1.11
 nose>=1.3.7
 nose-exclude>=0.5.0