Make `npm docs Raynos/after` work

when using git namespace dependencies in package.json which expand to either public or private git uris.

It would be nice if `npm docs {{githubNamespace}}` opened the github page for that project. 

This is very useful for private git dependencies because it means I can use `npm docs` as a uniform documentation opener between public npm dependencies and git uris
Typo: .get(project) not .get(n).
Typo: add project, not githubParts
the tests require docs to be made already

Otherwise the `make test` command fails to find ronn when generating the
docs for the first time in the prepublish step.

Probably there's a better way to do this, since tarball generation
requires a dev dep to be installed.  But this works on Unix at least,
and gets it by for now.