Change the README to remove the warning for 1.0.0 release
Change the README to remove the warning for 1.0.0 release

Change the README since the next release will be 1.0.0 and interfaces
will be considered stable.

Change-Id: I9d76e3f337985fec47943c984abd7f9efd0b06f3

sileht/keystoneauth,jamielennox/keystoneauth