reenable and fix tests, integrate nan for broader node version support

It compiles and the tests pass for me on mac os 10.10, with both node 0.10.32 and 0.11.14.  However, it looks like the tests don't actually hit the native code (advice on what tests could be added here is welcome).

I made sure to test both the "cheetah" and "lion" code paths (by editing the source to include the other file).  Both compile, at least.

I'm guessing the dates on the tests had been broken for a while since the tests were not enabled.  Let me know if that might be a machine-specific thing, somehow.