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

...oding}

https://jira.codehaus.org/browse/MPMD-165
This is of course awesome magic. The implicit operation is absolute safe. See [here](http://groovy.codehaus.org/api/groovy/util/CharsetToolkit.html). You could add a comment above though.