Bring travis configuration up to date

Author: hannesvdvreken

.travis.yml

@@ -1,22 +1,22 @@
-dist: trusty
-sudo: false
 language: php
-php:
-  - 5.5
-  - 5.6
-  - 7.0
-  - 7.1
-  - 7.2
-  - 7.3
-  - 7.4
-  - nightly
+os: linux
+dist: xenial
 
-matrix:
+jobs:
+  include:
+    - php: 5.5
+    - php: 5.6
+    - php: 7.0
+    - php: 7.1
+    - php: 7.2
+    - php: 7.3
+    - php: 7.4
+    - nightly
   allow_failures:
     - php: nightly
   fast_finish: true
 
-before_script:
+install:
   - composer install -n
 
 script: