Update package.json

Please add "win32" as supported OS. I do not expect compatibility problems between general windows and "win32".
Otherwise npm will not scussefull install the package on windows 8.1 platform

npm ERR! notsup Unsupported
npm ERR! notsup Not compatible with your operating system or architecture:
.0.1
npm ERR! notsup Valid OS:    linux,darwin,freebsd,windows
npm ERR! notsup Valid Arch:  any
npm ERR! notsup Actual OS:   win32
npm ERR! notsup Actual Arch: x64