porting gyp-build to libpifacedigital

[h0ru5]

@tompreston now maintains the c-lib as standalone as libpifacedigital. It does not have a install yet, I raised it there piface/libpifacedigital#9

would be a smoother experience for installing via npm, if there is a knwon location.

currently hacking the build-gyp accordingly, but it seems I also need to touch up the function names.