Merge pull request #94 from msciciel/msciciel

subscribe to repo only if install_from_repo variable is set to true

nginx/ng/install.sls

 
 {% if salt['grains.get']('os_family') == 'RedHat' %}
 nginx_yum_repo:
+  {%- if nginx.install_from_repo %}
   pkgrepo.managed:
+  {%- else %}
+  pkgrepo.absent:
+  {%- endif %}
     - name: nginx
     - humanname: nginx repo
     {%- if salt['grains.get']('os') == 'CentOS' %}