Change headers for rendering

... and make example into code-block with syntax definition

README.md

@@ -13,24 +13,24 @@ This roles requires an access token for the Zerotier API. This enables the role
 Role Variables
 --------------
 
-###zerotier_api_url
+### zerotier_api_url
 The url where the Zerotier API lives. Must use https protocol.    
 Default: https://my.zerotier.com
 
-###zerotier_accesstoken
+### zerotier_accesstoken
 The access token needed to authorize with the Zerotier API. You can generate one in your account settings on my.zerotier.com.
 
-###zerotier_network_id (required)
+### zerotier_network_id (required)
 The 16 character network ID of the network the new members should join.
 
 Example Playbook
 ----------------
 
-
+```yaml
     - hosts: servers
       vars:
          zerotier_network_id: 1234567890qwerty
          zerotier_accesstoken: "{{ vault_zerotier_accesstoken }}"
       roles:
          - { role: m4rcu5nl.zerotier }
-
+```