Reduce number of tests

Author: GuilhemN

.travis.yml

@@ -1,19 +1,12 @@
 language: php
 
-php:
-  - 5.3
-  - 5.6
-  - 7.0
-  - 7.1
-
 matrix:
   include:
-    - php: 5.6
+    - php: 5.3
       env: COMPOSER_FLAGS="--prefer-lowest" SYMFONY_DEPRECATIONS_HELPER=weak
     - php: 7.1
-      env: SYMFONY_VERSION='2.8.*'
     - php: 7.1
-      env: SYMFONY_VERSION='3.3.*'
+      env: SYMFONY_VERSION='2.8.*'
 
 sudo: false