Linux formula should be able to create non-unique users.

Change-Id: I3338950ed3726a750149d849d33813b0eeed50c0
diff --git a/README.rst b/README.rst
index f35bce7..cd9d5c2 100644
--- a/README.rst
+++ b/README.rst
@@ -50,6 +50,7 @@
             home: '/home/jdoe'
             home_dir_mode: 755
             email: 'jonh@doe.com'
+            unique: false
           jsmith:
             name: 'jsmith'
             enabled: true