build(travis): yield coverage.xml

Author: adhocore

.travis.yml

@@ -27,7 +27,7 @@ before_script:
   - for P in src tests; do find $P -type f -name '*.php' -exec php -l {} \;; done
 
 script:
-  - vendor/bin/phpunit --coverage-text
+  - vendor/bin/phpunit --coverage-text --coverage-clover=coverage.xml
 
 after_success:
   - bash <(curl -s https://codecov.io/bash)