Remove native code for Node >= 0.9.1

I'm a big fan of this project and have used it a few times. I noticed a few users having issues running it in restricted environments so I spent some time considering a JS-only version. As it turns out, since the addition of Timers.unref() in 0.9.1, we can safely unref the interval timer which will no longer keep the server open. 

In this pull request is a full conversion to a JS-only module as well as a few example fixes. All tests pass and the results are identical, with one small behavior change; the C module would start measuring lag *after* the first tick (from 500ms onward), while this module starts measuring lag on the first tick.