[.travis.yml] Refactor script

.travis.yml

@@ -1,10 +1,6 @@
 dist: trusty
+sudo: false
 language: php
-php:
-  - '5.6'
-  - '7.0'
-  - hhvm
-  - nightly
 
 before_install:
   # Circumvent a bug in current Travis CI builds using Ubuntu Trusty, where the
@@ -30,6 +26,13 @@ script:
 
 matrix:
   fast_finish: true
+
+  include:
+    - php: 5.6
+    - php: 7.0
+    - php: hhvm
+    - php: nightly
+
   allow_failures:
     - php: hhvm
     - php: nightly