update travis

Author: OxCom

.travis.yml

@@ -55,9 +55,10 @@ matrix:
             env: SYMFONY_VERSION=~4.2
 
 before_install:
-    - composer require roave/security-advisories:dev-master --no-update
-    - composer require symfony/symfony:${SYMFONY_VERSION} --no-update
-    - php -dmemory_limit=-1 composer update
+    - curl -s https://getcomposer.org/installer | php
+    - php composer.phar composer require roave/security-advisories:dev-master --no-update
+    - php composer.phar require symfony/symfony:${SYMFONY_VERSION} --no-update
+    - php -dmemory_limit=-1 composer.phar update
 
 script:
     - cat composer.json | grep symfony\/symfony