Fix travis build

.travis.yml

@@ -1,12 +1,17 @@
 language: php
 
-php:
-  - 5.4
-  - 5.5
-  - 5.6
-  - 7.0
-  - 7.1
-#  - hhvm
+matrix:
+  fast_finish: true
+  include:
+    - php: "7.3"
+    - php: "7.2"
+    - php: "7.1"
+    - php: "7.0"
+    - php: "5.6"
+    - php: "5.5"
+      dist: trusty
+    - php: "5.4"
+      dist: trusty
 
 # faster builds on new travis setup not using sudo
 sudo: false