Update .travis.yml

Author: shabbyrobe

.travis.yml

@@ -4,15 +4,32 @@ before_install:
   - git submodule update --init
   - composer install
 
-php:
-  - "hhvm"
-  - "nightly"
-  - "7.1"
-  - "7.0"
-  - "5.6"
-  - "5.5"
-  - "5.4"
-  - "5.3"
+matrix:
+  include:
+  - dist: precise
+    php:
+      - "nightly"
+      - "7.1"
+      - "7.0"
+      - "5.6"
+      - "5.5"
+      - "5.4"
+      - "5.3"  
+  - dist: trusty
+    php:
+      - hhvm-3.3
+      - hhvm-3.6
+      - hhvm-3.9
+      - hhvm-3.12
+      - hhvm-3.15
+      - hhvm-3.18
+      - hhvm-nightly
+      - "nightly"
+      - "7.1"
+      - "7.0"
+      - "5.6"
+      - "5.5"
+      - "5.4"
 
 branches:
   only:
@@ -24,4 +41,5 @@ script: php test.php
 matrix:
   allow_failures:
   - php: "nightly"
+  - php: "hhvm-nightly"