Make AS number and neighbors optional in BgpRouter

Change-Id: Ib1af1a97b69e5aba52b234dd4a082eeacaa97f2a
diff --git a/routinglib.py b/routinglib.py
index b7424ca..eab92c2 100644
--- a/routinglib.py
+++ b/routinglib.py
@@ -310,7 +310,7 @@
     """Quagga router running the BGP protocol."""
 
     def __init__(self, name, interfaces,
-                 asNum, neighbors, routes=[],
+                 asNum=0, neighbors=[], routes=[],
                  defaultRoute=None,
                  quaggaConfFile=None,
                  zebraConfFile=None,