Merge pull request #17 from michaelkuty/feature/api_ssl

Support letsencrypt certs for API.

salt/files/_api.conf

   port: {{ api.bind.port }}
   host: {{ api.bind.address }}
   {%- if api.get('ssl', {}).get('enabled', False) %}
-  {%- if api.ssl.engine == 'salt' %}
+  {%- if api.ssl.engine == 'letsencrypt' %}
+  ssl_crt: /etc/letsencrypt/live/{{ api.ssl.name }}/cert.pem
+  ssl_key: /etc/letsencrypt/live/{{ api.ssl.name }}/privkey.pem
+  {%- elif api.ssl.engine == 'salt' %}
   ssl_crt: /etc/ssl/certs/{{ system.name }}.{{ system.domain }}.crt
   ssl_key: /etc/ssl/private/{{ system.name }}.{{ system.domain }}.key
   {%- else %}