Add ability to repackage project JAR

[bspeice]

Thanks so much for this project! It's been awesome so far.
The only feature I could use that doesn't seem to be present is repackaging JARs from local projects. I.e., the following fails:

compile jarjar.repackage {
    from project(':mylocalproject')
    classRename 'original.name.**', 'new.name.@1'
}

Is it possible for this to be added?