Allow root directory to be overridden via environment variable

README.md

@@ -8,3 +8,6 @@
 * nginx.conf.erb - Optional File: overrides `conf/nginx.conf.erb`
 * mime.types - Optional File: overrides `conf/mime.types`
 * custom-build - Optional File: executes commands before build is finished
+
+## Environment Variables
+* root - Optional: overrides root directory

conf/nginx.conf.erb

@@ -12,7 +12,7 @@ http {
 	server {
 		listen <%= ENV['PORT'] %>;
 		server_name  _;
-		root /app/www;
+		root <%= ENV.fetch('root', '/app/www') %>;
 		index index.html;
 	}
 }