binary files configuration option

Hi Benjamin,

would you consider merging my binary_files_configuration branch into your master?
I'd appreciate a new release of your plugin after the merge.

Since this is my first groovy code, you really should review it. It is mostly copy and paste based on the ```configFiles``` closure, it works for me, but maybe I forgot something... .

Also see https://github.com/bmuschko/gradle-cargo-plugin/issues/31.

Thanks a lot,
Sascha