Relates: #46
* Allow phpcbf / diff to be optional, as not all tests are fixable. * Provide more information in case of error. * Provide phpunit dist to run phpunit without anything special. Relates: #46
* Add diff to test actual fixes. Relates: #46
* Parses fixtures to auto run tests for sniffs. * Compares actual result for fixture input against expected result from fixture. Relates: #46