feature: intercept object access about gorilla-claw

[talss89]

May need to refactor HookProxy a bit for this. Detecting calls doesn't require a proxy, but detecting property access does.

Need to ensure HookProxy can proxy another HookProxy recursively too. Unsure if this works currently - not tested.

[talss89]

Recursive HookProxy test now in branch, and is passing.

    public function testRecursiveProxy() {
        $obj = new MockClass(3);
        $proxy_1 = new HookProxy(function($input) {return $input . '-proxy_1';}, $obj);
        $proxy_2 = new HookProxy(function($input) {return $input . '-proxy_2' . '-' . $this->{'id'};}, $proxy_1);

        $this->assertEquals("test-proxy_2-3", $proxy_2->___cb("test"));
    }
}