Major Description
Add the ability to set the maximum number of allowed violations before a build fails.
The idea being that you could set a threshold of errors before the build would actually fail, instead of the default of 1. This would be useful for legacy code that had not always been using PMD and needs to be cleaned up over time. If the value is set then the code can't get worse and people can use it to help clean up their projects.
This is similar to the checkstyle property http://maven.apache.org/plugins/maven-checkstyle-plugin/check-mojo.html#maxAllowedViolations
PR: https://github.com/apache/maven-pmd-plugin/pull/1