Use constraints in tox.ini
Use constraints in tox.ini

As per email [1] from Andreas, we can add upper constraints
on packages used now.

[1] http://openstack.markmail.org/thread/a4l7tokbotwqvuoh

Change-Id: Id78c66c8fdd52802e2018214a7a5bfa1616aeaab

openstack/senlin-dashboard,stackforge/senlin-dashboard,openstack/senlin-dashboard,openstack/senlin-dashboard,openstack/senlin-dashboard,stackforge/senlin-dashboard,stackforge/senlin-dashboard