Use pip (and DevStack) instead of setuptools in docs
Use pip (and DevStack) instead of setuptools in docs

The docs instruct you to install pip, and then document the use of
setuptools, which pbr doesn't particularly support. But pip alone will
fail, so I added a note referencing devstack if you need help on that
step.

Change-Id: Iea07b5ffd9d5c6c8509a698db2728e0fde21d4d8

ilay09/keystone,openstack/keystone,dims/keystone,klmitch/keystone,openstack/keystone,rajalokan/keystone,ilay09/keystone,openstack/keystone,rajalokan/keystone,dims/keystone,mahak/keystone,cernops/keystone,himanshu-setia/keystone,mahak/keystone,klmitch/keystone,ilay09/keystone,rajalokan/keystone,cernops/keystone,mahak/keystone,himanshu-setia/keystone