updated travis config

Author: chirimoya

.travis.yml

@@ -7,15 +7,25 @@ env:
 matrix:
   include:
     - language: php
-      php: 7.1
+      php: 5.6
       env:
         - SYMFONY_VERSION=2.8.*
 
     - language: php
-      php: 7.1
+      php: 5.6
+      env:
+        - SYMFONY_VERSION=3.4.*
+
+    - language: php
+      php: 7.0
       env:
         - SYMFONY_VERSION=3.4.*
 
+    - language: php
+      php: 7.1
+      env:
+        - SYMFONY_VERSION=4.0.*
+
     - language: php
       php: 7.2
       env: