Just a heads up that these extensions will stop working soon.

https://twitter.com/mdo/status/830149416556191744

Most of these extensions popping up that revert GitHub's header to white are simply removing the `.header-dark` class which (currently) applies the dark styles and according to @mdo the styles will be permanently applied as a default.

The only way to revert them after this would be to reapply the old styles so if someone really wants that they might want to save them now.