Update example playbooks for using new roles

ansible/docker.yml

@@ -0,0 +1,5 @@
+---
+- hosts: docker-host
+  become: yes
+  roles:
+    - docker

ansible/hosts

@@ -19,6 +19,12 @@ sub.domain.com:22
 sub.domain.com:22
 127.0.0.1:22
 
+[nginx-server]
+sub.domain.com:22
+
+[docker-host]
+127.0.0.1:22
+
 ## green.example.com
 ## blue.example.com
 ## 192.168.100.1

ansible/nginx.yml

@@ -1,6 +1,5 @@
 ---
-- hosts: nginx
+- hosts: nginx-server
   become: yes
   roles:
   - nginx
-  - core