The Adtran OLT Adapter requires the zeroMQ protocol provided by the twisted txZMQ package

Change-Id: If2e5ee9ba8b01d1b938ad5e8c3261d4123720a77
diff --git a/requirements.txt b/requirements.txt
index 62f79fd..c63fc59 100755
--- a/requirements.txt
+++ b/requirements.txt
@@ -44,6 +44,9 @@
 pyang>=1.7
 lxml==3.6.4
 nosexcover==1.0.11
+zmq>=0.0.0
+pyzmq>=16.0.2
+txZMQ==0.8.0
 dicttoxml
 
 # python-consul>=0.6.1  we need the pre-released version for now, because 0.6.1 does not