Updating getting started docs

Updating to reflect CLI change to Assembly create command

See the following bug for details on the CLI change
https://bugs.launchpad.net/python-solumclient/+bug/1332315

Change-Id: I72a3fa29ac7a3a1a507ef9169f85bf1d7285fb87
Closes-Bug: #1336348
Merge "Updating getting started docs"