Create 1.4.0 release notes
Create 1.4.0 release notes

Change-Id: I2fa7d7875518ceebbdc3936eedfe72d17c81535f

BjoernT/python-openstackclient,BjoernT/python-openstackclient,dtroyer/python-openstackclient,dtroyer/python-openstackclient,redhat-openstack/python-openstackclient,openstack/python-openstackclient,redhat-openstack/python-openstackclient,openstack/python-openstackclient