Updates Travis to use compatible OSes

.travis.yml

@@ -2,19 +2,22 @@ language: php
 
 sudo: false
 
-dist: xenial
+jobs:
-
+  include:
-php:
+  - dist: trusty
-  - 5.4
+    php:
-  - 5.5
+    - 5.4
-  - 5.6
+    - 5.5
-  - 7.0
+  - dist: xenial
-  - 7.1
+    php:
-  - 7.2
+    - 5.6
-  - 7.3
+    - 7.0
-  - 7.4
+    - 7.1
-  - nightly
+    - 7.2
-  - hhvm
+    - 7.3
+    - 7.4
+    - nightly
+    - hhvm
 
 matrix:
     allow_failures: