Update phpunit invocation for Travis

- No longer need the `-c ./test/` directive.

Author: weierophinney

.travis.yml

@@ -10,7 +10,7 @@ before_script:
   - composer install --dev --prefer-source
 
 script:
-  - ./vendor/bin/phpunit -c ./test --coverage-clover ./build/logs/clover.xml
+  - ./vendor/bin/phpunit --coverage-clover ./build/logs/clover.xml
   - ./bin/check-cs.sh
 
 after_script: