Upgrade Nginx to v1.13.1

Author: rtucek

Dockerfile

@@ -13,7 +13,7 @@ LABEL \
 	org.label-schema.version=${VERSION}
 
 ENV \
-	NGINX_VERSION=1.13.0 \
+	NGINX_VERSION=1.13.1 \
 	PHP_VERSION=7.1.5 \
 	XDEBUG_VERSION=2.5.4 \
 	VERSION=${VERSION}