Use trusty for PHP 5.5

Author: W0rma

.travis.yml

@@ -1,7 +1,6 @@
 language: php
 
 php:
-    - 5.5
     - 5.6
     - 7.0
     - 7.1
@@ -22,6 +21,9 @@ matrix:
         - php: 5.4
           dist: precise
           sudo: required
+        - php: 5.5
+          dist: trusty
+          sudo: required
 
 # faster builds on new travis setup not using sudo
 sudo: false