Added Symfony 2.7 to build

Author: dantleech

.travis.yml

@@ -14,12 +14,14 @@ matrix:
     - env: SYMFONY_VERSION=dev-master
     - php: hhvm
   include:
-    - php: 5.5
-      env: SYMFONY_VERSION=2.3.*
-    - php: 5.5
+    - php: 5.6
       env: SYMFONY_VERSION=2.4.*
-    - php: 5.5
-      env: SYMFONY_VERSION=dev-master
+    - php: 5.6
+      env: SYMFONY_VERSION=2.5.*
+    - php: 5.6
+      env: SYMFONY_VERSION=2.6.*
+    - php: 5.6
+      env: SYMFONY_VERSION=2.7.*
 
 before_script:
   - composer self-update