Add docs about database being dropped during provisioning

README.rst

@@ -58,6 +58,9 @@ a minimum of 2 CPUs and 4GB of memory works well.
    services with superusers (for development without the auth service) and
    tenants (for multi-tenancy).
 
+   **Note** When running the provision command databases for all systems will be
+   dropped and recreated.
+
    The username and password for the superusers are both "edx". You can access
    the services directly via Django admin at the ``/admin/`` path, or login via
    single sign-on at ``/login/``.
@@ -74,6 +77,7 @@ a minimum of 2 CPUs and 4GB of memory works well.
 
        make dev.provision
 
+
 3. Start the services. This command will mount the repositories under the
    DEVSTACK\_WORKSPACE directory.