Merge pull request #98 from outime/master

Adds 'empty_password' statement for states.user.present (issue #97)

pillar.example

     fullname: B User
     password: $6$w.............
     enforce_password: True
+    # WARNING: If 'empty_password' is set to True, the 'password' statement
+    # will be ignored by enabling password-less login for the user.
+    empty_password: False
     home: /custom/buser
     createhome: True
     roomnumber: "A-1"

users/init.sls

     {% if 'password' in user -%}
     - password: '{{ user['password'] }}'
     {% endif -%}
+    {% if user.get('empty_password') -%}
+    - empty_password: {{ user.get('empty_password') }}
+    {% endif -%}
     {% if 'enforce_password' in user -%}
     - enforce_password: {{ user['enforce_password'] }}
     {% endif -%}