Add vanilla example (caddyserver#99)

Author: Aaron Ellington

vanilla/Caddyfile

@@ -0,0 +1,11 @@
+forum.example.com {
+    root /var/www/vanilla/
+
+    fastcgi / /run/php/php7.0-fpm.sock php {
+        index index.php
+    }
+
+    rewrite {
+        to {path} /index.php?p={path}&{query}
+    }
+}

vanilla/README.md

@@ -0,0 +1,6 @@
+# [Vanilla](https://open.vanillaforums.com/)
+
+**Considerations:**
+- You may need to change the `fastcgi` endpoint to the listen address of your `php-fpm` instance
+- Make sure that the user that Caddy is running under has permissions to to `php-fpm`
+- Make sure that the user that `php-fpm` is running under has permissions to the `root` directory