Allow removal of hooks

[nathanrice]

It would be nice if you could disable certain hooks from being used in this plugin. see #12.

[deckerweb]

When allowing of hooks should be allowed then adding of other hooks from third-party plugins should also be possible.

Therefore I suggest making the array of hooks filterable - so developers can add or remove certain hooks.

Thanks a lot in advance! :)

[nathanrice]

I don't love the hard coded method we use here. I'd rather we just detect what's on any given hook, and give the option to unhook.