Allow xdebug not to be disabled

This allows the script to continue if xdebug can't be disabled
(most likely bc it isn't there in the first place)

.travis.yml

@@ -16,7 +16,7 @@ matrix:
 sudo: false
 
 before_script:
-  - phpenv config-rm xdebug.ini
+  - phpenv config-rm xdebug.ini || true
   - composer self-update
   - composer require satooshi/php-coveralls:~2.0.0 --no-update --dev
   - composer install --prefer-source