fix(init): replace gid_from_name (deprecated in develop)

* Close #198
* All details in that issue
* Solution based upon:
  - saltstack-formulas/vault-formula#35 (comment)

Author: myii

users/init.sls

@@ -144,7 +144,7 @@ users_{{ name }}_user:
     {% elif 'prime_group' in user and 'name' in user['prime_group'] %}
     - gid: {{ user['prime_group']['name'] }}
     {% else -%}
-    - gid_from_name: True
+    - gid: {{ name }}
     {% endif -%}
     {% if 'fullname' in user %}
     - fullname: {{ user['fullname'] }}