update for node v0.11.13

this uses a slightly modified version of nan-1.0.0.

the reason is because we need a reference to our weak object.
obviously, if we save another persistent reference and don't make it weak, it simply won't ever be gc'ed.
we're using nan to abstract out the node api, so it'd be silly to roll our own `SetWeak`

so, @rvagg in some cases it's optimal to have a reference to your persistently-weak reference. so, because I don't know the direction you might want to take, I just did a quick hack for this to work by making things public. please have a look at the diff to see what I mean. the changes to nan.h are the following:

1. make `_NanWeakCallbackInfo<T, P>* info_` public in `_NanWeakCallbackData`
2. `NanMakeWeakPersistent` now returns `_NanWeakCallbackInfo<T, P>*`