Drops php 5.4 and 5.5 and tests maintained version of symfony

Author: Keith Kirk

.travis.yml

@@ -7,21 +7,17 @@ cache:
         - $HOME/.composer/cache/files
 
 php:
-    - 5.4
-    - 5.5
     - hhvm
-    
+
 matrix:
     fast_finish: true
     include:
-        - php: 5.6
-          env: SYMFONY_VERSION=2.3.*
-        - php: 5.6
-          env: SYMFONY_VERSION=2.6.*
         - php: 5.6
           env: SYMFONY_VERSION=2.7.*
         - php: 5.6
           env: SYMFONY_VERSION=2.8.*
+        - php: 5.6
+          env: SYMFONY_VERSION=3.4.*
         - php: 7.0
           env: COVERAGE=yes
     allow_failures: