Update .travis.yml

Author: Webklex

.travis.yml

@@ -1,17 +1,30 @@
 language: php
 
 php:
+  - 5.6
   - 7.0
   - 7.1
   - 7.2
   - 7.3
+  - hhvm
 
 matrix:
-  fast_finish: true
+  fast_finish: true 
+  allow_failures:
+   - php: 5.6
+   - php: hhvm
 
 sudo: false
 
-install: composer install --no-interaction
+before-install:
+ - composer self-update
+ - composer install --prefer-source --no-interaction --dev
+
+install: 
+ - composer install --no-interaction
+
+script:
+ - phpunit
 
 notifications:
   email: