libxml fix

• #90 "load configuration even if libxml entity loader is disabled"
• in the meantime, phpunit was fixed for #89

PHPUnit 4.x compatibility

This tag is to indicate the compatibility to PHPUnit 4.x.

Further changes since v0.6.1:

• new option --stop-on-failure
• new option --exclude-group
• test loading improvements (non PSR-0)
• some minor bugfixes