Remove deprecated PHP 5.3 to 5.6

Author: emulienfou

.travis.yml

@@ -2,9 +2,7 @@ language: php
 
 matrix:
   include:
-    - php: 5.3
-      env: COMPOSER_FLAGS="--prefer-lowest" SYMFONY_DEPRECATIONS_HELPER=weak
-      dist: precise
+    - php: 5.6
     - php: 7.1
     - php: 7.2
     - php: 7.1