Node 0.11.x support

With these changes, node_mdns builds and runs under Node 0.11.14 and nan 1.3 although I cannot say with certainty as amount of testing it received with these changes is too little.
Good catch. Looks like nan is missing exactly the specialization we need. Pretty sure the compiler picks the generic version:

https://github.com/rvagg/nan/blob/master/nan.h#L186
https://github.com/rvagg/nan/blob/master/nan.h#L1073

... which is not what we want. Two options:

1. Refactor and use `NanNew<Uint32>(...)`. This will hit https://github.com/rvagg/nan/blob/master/nan.h#L313 and might just work.
2. Get with the nan guys, open an issue, &c.