Uses Symfony 4.0.* instead the dev version for the "stable" builds

Author: sroze

.travis.yml

@@ -23,7 +23,7 @@ matrix:
     - php: 7.1
       env: DEPS=dev SYMFONY_VERSION='3.4.*'
     - php: 7.1
-      env: DEVS=dev SYMFONY_VERSION='4.0.x-dev'
+      env: DEVS=dev SYMFONY_VERSION='4.0.*'
   allow_failures:
     - php: 7.1
       env: SYMFONY_VERSION='4.0.x-dev'