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.
tilde (or that godawful caret) is good for **NAN**, we only do bug fixes in patch releases and promise not to break anything there. Minor versions are mostly safe as well, but stuff can get deprecated for good reasons. Major versions can do anything.