Make python mistralclient readme better
Make python mistralclient readme better

Adding some line breaks to make the README file better.

Change-Id: Ic42f6fa3e6a83cb0c4c3a5a324611411d2df7a1e

openstack/python-mistralclient,StackStorm/python-mistralclient,StackStorm/python-mistralclient,openstack/python-mistralclient