Node js C++ Addon Overload Resolution - v0.7.0

Another minor release but with a major new type!

- AsyncCallback - this is a new type the module exposes, it allows a stand alone thread to do callbacks into v8 by queuing the call data and signalling libuv to execute it next time the event loop executes, by far the most useful feature of this release!

Note that there is an option to change the callback from weak to strong and by that making node js wait until the callback is destroyed before exiting making it useful in many situations.

- expose get_type to classes outside the node-overload resolution - while its very beneficial to hide most of the type information from classes using this module, in some cases such as property accessors which don't pass through the module but still need to make sure the data types passed to them is the one expected, get_type exposes this functionality.

- fix array convertible checks - when using arrays, the old method wasn't checking the correct conversion is possible from array types to other array types. while it is possible to convert array to number (in JavaScript anything is possible ;-) ), it should not be considered as a valid convertible but now it is also allowed to convert an array of derived to array of base. Tags: