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.
Previously, setTimeout(fn, 0) would create a new Timer() object,
which has a close() method (and is a bit slower). The recent
change to more closely emulate browser setTimeout behavior dodges
this path, so this assertion is no longer valid.