watchify ignores paths option passed to browserify on update

[laurencedorman]

When watchify fires the 'update' event, calling b.bundle() produces errors that would not happen if b.paths option was being taken into account - indeed, the bundle compiles the first time around because of this.

This error can only be observed when saving a file within a local npm module that has been symlinked into the node_modules folder of an app.