[MPMD-165] target/site/pmd.html created with invalid charset=${outputEnc...

...oding}

https://jira.codehaus.org/browse/MPMD-165
The integration test ran fine. I also was bit surprised that it works - and it appears, that Groovy's getText() ([1]) method guesses ([2]) the encoding.
It might be safer though to use getText("UTF-16") - as I'm not sure, whether the BOM will always be written. At least, this is for me the case and that's why Groovy correctly guesses the encoding.

[1]: https://github.com/groovy/groovy-core/blob/master/src/main/org/codehaus/groovy/runtime/ResourceGroovyMethods.java#L595
[2]: https://github.com/groovy/groovy-core/blob/master/src/main/groovy/util/CharsetToolkit.java#L162