Laravel 5.6 updates

Travis config update

Removed HHVM script as Laravel no longer support HHVM after releasing 5.3

vendor/symfony/http-kernel/Bundle/BundleInterface.php

@@ -46,19 +46,6 @@ interface BundleInterface extends ContainerAwareInterface
      */
     public function getContainerExtension();
 
-    /**
-     * Returns the bundle name that this bundle overrides.
-     *
-     * Despite its name, this method does not imply any parent/child relationship
-     * between the bundles, just a way to extend and override an existing
-     * bundle.
-     *
-     * @return string The Bundle name it overrides or null if no parent
-     *
-     * @deprecated This method is deprecated as of 3.4 and will be removed in 4.0.
-     */
-    public function getParent();
-
     /**
      * Returns the bundle name (the class short name).
      *