Fix that travis build

Author: Krasnoperov Vitaliy

.travis.yml

@@ -1,9 +1,11 @@
 language: php
-php:
-  - '5.3'
-  - '5.6'
-  - '7.0'
-  - '7.1'
-  - hhvm
+matrix:
+  include:
+    - php: 5.3
+      dist: precise
+    - php: 5.6
+    - php: 7.0
+    - php: 7.1
+    - php: hhvm
 
 script: python tests/tests.py