Add single coute to version docker-compose

src/Docker/Composer/FileFormat.php

@@ -68,7 +68,7 @@ class FileFormat
      */
     function render()
     {
-        $rtr = array("version" => $this->version, "services" => array());
+        $rtr = array("version" => "'" . $this->version . "'", "services" => array());
         foreach ($this->services as $name => $service) {
             $rtr["services"][$name] = $service->getConfig();
         }