Update sl-blip dependency during release

A series of small changes that allows `slt-release` to replace `npm version` with `slt version set` which does exactly what is needed.

First planned use is strongloop-internal/scrum-nodeops#182

@sam-github @bajtos you have been the main reviewers.. one of you want to take a look at this?
Use of original was inherited from the test I used as a starting point. The purpose is to be sure that what is being compared is what is on disk, to prevent any false positives or negatives.