Use phpunit.xml.dist instead

Providing a phpunit.xml.dist instead allows developers to chose whether to use your configuration or their own. Ignoring a phpunit.xml within a repo means they can use the settings they want.

Reference:
http://www.testically.org/2010/08/24/best-practice-how-to-ship-phpunit-configuration/
https://github.com/caefer/StreamHitching/commit/e1a6cef49ea6466403e3aea533728e04139e5d80