Remoting support

Due to I were needed both remoting support and changeLog appending, this pull request is based on [my previous changes](https://github.com/jenkinsci/testfairy-plugin/pull/1). Please review it before this change.

This change adds ability to run on jenkins slave nodes. Before this change testfairy plugin failed immediately because it was looking for apk to upload on a master node in (most likely) unexisting workspace - this is due to my jobs being spreaded around slave nodes.