Workflow for testing packages downstream

[matt-gadd]

Being able to test/try in progress packages in downstream dependencies is currently a slow and reasonably complicated process involving our actual release tool (see https://github.com/dojo/dojo.io/pull/332/files/a0b8e942a280a238ce9e15b698b1df89fb288bb5#r154390172).

This didn't used to be the case when our grunt link/npm link workflow worked. We should investigate what it would take to get npm link working again so a developer can simply run a link once and then work as normal.

[kitsonk]

Where did we get with this? If it isn't being worked on, we should unassign it and move it back to ToDo

[umaar]

Oh sorry I haven't looked at this yet!