Travis: Don't test vendor PHP files

.travis.yml

@@ -14,7 +14,7 @@ matrix:
   fast-finish: true
 
 script:
-  - find . -type f -name '*.php' -print0 | xargs -0 -I file php -l file > /dev/null
+  - find . -not \( -path './vendor' -prune \) -type f -name '*.php' -print0 | xargs -0 -I file php -l file > /dev/null
 
 before_deploy:
   - composer install