Fixed running tests in PHP 5.4 and PHP 5.5 in CI

Author: grogy

.travis.yml

@@ -1,13 +1,16 @@
 language: php
 
 php:
-  - 5.4
-  - 5.5
-  - 5.6
-  - 7.0
-  - 7.1
-  - 7.2
-  - 7.3
+  include:
+    - php: 5.4
+      dist: trusty
+    - php: 5.5
+      dist: trusty
+    - php: 5.6
+    - php: 7.0
+    - php: 7.1
+    - php: 7.2
+    - php: 7.3
 
 sudo: false