Make require('config/defer') syntax work

I had presumed this worked before, it is difficult to test this from inside
of the project itself. Manual testing from outside the project tree
confirmed that part of the parth after the "/" resolved relative to the
"config" directory where this package is stored, not the lib/ directory
where config.js is stored.

I built this work on top on top of my previous pull request to bind the defer
functions to the main config object when called.