Make friendly with DRY jenkins plugin

Did some researching, and the only difference I could find between the `DRY` plugin's [tests](https://github.com/jenkinsci/dry-plugin/blob/master/src/test/resources/hudson/plugins/dry/parser/cpd/cpd.xml) and the `duplication.xml` that `objective-ci` generates was the `encoding` attribute on the xml root node. The binaries `objective-ci` uses end up with `MacRoman`, and the tests use `UTF-8` -- switching to `UTF-8` seems to play nice with both the `violations` and the `DRY` plugins.