Alternative registry, plus Win32 fixes

Hi.
Changes:
 - `repos` object in `workspace.json` used where matched to add `--registry` flag to `npm i`
 - handles Windows bugs where `npm` has been installed via `npm`
 - all tests pass under Windows 7

I realise this might come under one of the "This is __not__" cases, but it seems an innocuous and small change. It helps a lot when you have one or two dependencies from a non `registry.npmjs.org` source.