fixed for node 0.11.5 using NODE_SET_METHOD

Hi,

I found this awesome module yesterday while researching for ways to get better error stack traces for my generators library [genny](https://github.com/spion/genny). Great work!

However in node v.0.11.5 (released yesterday) trying to include galaxy-stack results with the following:

    node: symbol lookup error: /home/spion/Documents/galaxy-stack/build/Release/galaxy_stack.node: undefined symbol: _ZN2v816FunctionTemplate3NewEPFNS_6HandleINS_5ValueEEERKNS_9ArgumentsEES3_NS1_INS_9SignatureEEEi

symbol name being

    v8::FunctionTemplate::New(v8::Handle<v8::Value> (*)(v8::Arguments const&), v8::Handle<v8::Value>, v8::Handle<v8::Signature>, int)

when ran through c++filt

There seems to be a deprecation warning about this, so I switched everything to NODE_SET_METHOD. Also 

    using namespace v8;

caused a clash when I tried to use NODE_SET_METHOD-compatible functions that take `v8::FunctionCallbackInfo`, so I switched the code to explicit namespaces everywhere.

The result compiles and works with both 0.11.4 and 0.11.5 without deprecation warnings :)