Constants moved to message.py.
Constants moved to message.py.

Update issue 13

m-lab/mlab-ns,m-lab/mlab-ns,fernandalavalle/mlab-ns,m-lab/mlab-ns,fernandalavalle/mlab-ns,m-lab/mlab-ns,fernandalavalle/mlab-ns,fernandalavalle/mlab-ns