Added macro for defining gc callbacks.
Added tests for gc callbacks.
Linted
Merge pull request #184 from rvagg/lint

Linted
switch to plain MIT license
fix license ownership
Update gc.cpp
Merge pull request #182 from rvagg/gc_callback

Added macro for defining gc callbacks.
Merge pull request #183 from rvagg/performance

Removed unnecessary local handle creation.
Added test target to Makefile
Removed unnecessary handle creation in NanMakeCallback
Added const-ness to references in NanHasInstance