node-gyp: make aware of nightly, next-nightly & rc

A temporary fix only, node-gyp needs to be made more intelligent
upstream about figuring out where to find the download file by
inspecting the binary.

Floating patch on npm.

PR-URL: nodejs#2066
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: Ryan Graham <r.m.graham@gmail.com>

Author: rvagg