more generic, merge in prebuildify-load

[juliangruber]

I wrote https://github.com/juliangruber/prebuildify-load as a replacement for this module which isn't build system dependant (my module uses cmake-js). I propose to advice to use prebuildify-load as the main module.

This issue goes hand in hand with prebuild/prebuildify#7.

[dvc94ch]

@mafintosh Thoughts on a) making this build tool independent and b) renaming it to prebuildify-load?