Fix building on Windows 7 x64

- tried the fix listed here, and it worked: https://groups.google.com/forum/#!topic/nodejs/onA0S01INtw
- have not proved that it will work everywhere, but it's worth a shot

Related to #46.

EDIT: I forgot to mention, you should probably switch the order of #includes in cpu_profiler.h as well, and maybe add `#include <node.h>` to all your .cc files.  I'm not sure.