Use trusty distribution since Xenial does not support PHP 5.4, 5.5

MBriedis · MBriedis · commit 368722e87e9d · 2019-09-09T16:02:21.000+03:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,5 +1,6 @@
 language: php
 sudo: false
+dist: trusty
 
 env:
   - COMPOSER_DISABLE_XDEBUG_WARN=1
