docs: pip install -e needs an argument
docs: pip install -e needs an argument

The arguments to install the development branch is incorrect, since
the -e option needs a directory to look for setup.py in.

Change-Id: Icfe402e7b79a50ddc885c7eadb6c323c27e36ef3

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