Use locally installed phpunit

Author: pelmered

.travis.yml

@@ -9,7 +9,7 @@ before_script:
   - travis_retry composer update --no-interaction --prefer-source
 
 script:
-  - phpunit --coverage-text --coverage-clover=coverage.clover
+  - vendor/bin/phpunit --coverage-text --coverage-clover=coverage.clover
 
 after_script:
   - wget https://scrutinizer-ci.com/ocular.phar