The copyright and license notice is already in the LICENSE file. There
is no justifiable reason to also require that it be included in every
file, since the individual files are not individually distributed except
as part of the entire package.
onExit() is similar to the onLoad() callback. onExit() is called on each
module just before the process exits. This can be used to check state in
unit tests, but not to perform I/O. The process will forcibly exit as soon
as all of the onExit callbacks are made.
There is one major API change in the refactor: filename extensions are now
required when requiring or including modules.
Added extra test to test-module-loading.js.