Install template from cache only

As `hoodie new` takes forever (especially when doing integration tests locally) I wrote some logic that forces npm to use the local cache if available.

Unfortunately npm's `--no-registry` command is currently broken, so it doesn't really work (https://github.com/npm/npm/issues/1738, https://github.com/npm/npm/issues/2568) but it will once they fix it, which is high on their agenda. Merging now would do no harm anyways.

Btw, there could be one workaround to make it work now: Create a local webserver that returns an error instantly and set it as npm's registry.

@svnlto