Ah, when you said "deregister hooks" I thought you meant provide a way to deregister from receiving `on_change` notification.  I didn't realize you meant rspec's before/around/after hooks.

Hmm....I'm a bit on the fence about this.  I feel like that if we're going to support mutating the metadata after-the-fact as a public API, we should fully support it.  OTOH, I'm OK stating that it's not intended to be a public API but is just intended for use by rspec-rails and is subject to change in a minor release.

Thoughts from others?

/cc @alindeman @xaviershay @samphippen @soulcutter