try to fix build

Author: Zordius Chen

.travis.yml

@@ -1,4 +1,6 @@
 language: php
+dist: trusty
+sudo: required
 php:
   - 5.4
   - 5.5
@@ -16,8 +18,6 @@ script:
   - vendor/bin/phpunit --coverage-clover=coverage.clover
   - build/travis_push
 
-sudo: false
-
 env:
   global:
     secure: "Wlez8f9yijTGs4heE9YrBWsEssDKwSqKld5pTcgYNwoSOAue8MmG/g/60ayyWXRBXiGmNQfiHsBSGw9v9Stn7vKKXzGROc2T34ERLkBi2AtifFw6vJK0VrK2EpcWTvgHPLeNlln+gIrA/oHliW4AKX9aUwIBV/MTPjd2A85RBn8="