Minor edits to the developing doc
Minor edits to the developing doc

The tools/with_venv.sh no longer exists in the source tree. This
patch cleans up all references to it.

Closes-Bug: #1514792

Change-Id: I4638c9894fab01b4556ee0537bf40807a659e7e9

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