Add JSON serialization hooking features.

Fixed a name collision bug. Unless someone else is starting their variables with HOOK, we shouldn't have any more name collisions.

Minor changes.

Added support for variadic functions. Now requires PHP7.

HookPHP works in HHVM!

Fixed a returning by reference error.

Some minor improvements, and real tests.

When you update, you'll have to refactor your calls from H:: to Hook::.

First release!