Add php 7.2 (#14)

Author: BrainMaestro

.travis.yml

@@ -5,6 +5,7 @@ matrix:
         - php: 5.6
         - php: 7.0
         - php: 7.1
+        - php: 7.2
     fast_finish: true
 
 before_install:
@@ -15,4 +16,4 @@ install:
 
 script:
   - composer validate --strict --no-check-lock
-  - phpunit
+  - ./vendor/bin/phpunit