Tighten requirements on cmd2

Work around for
https://bitbucket.org/catherinedevlin/cmd2/issue/6/packaging-bug

Change-Id: I8a18825d0660c21649a8d838635832959eee8a40
prepare for release 1.4.1

Change-Id: I192f5a7a8e21a097b2e501995a7e2d90c5dbbea8