Update .travis.yml

Author: barryvdh

.travis.yml

@@ -27,7 +27,7 @@ install:
   - phpenv rehash
 
 script:
-  - vendor/bin/phpunit --coverage-clover=coverage.clover
+  - phpunit --coverage-clover=coverage.clover
 
 after_script:
   - wget https://scrutinizer-ci.com/ocular.phar