make this library actually work

[jonathanong]

this library doesn't work on linux since you're using the 32-bit binary.

i can't seem to open a pull request, maybe because i worked on master on my branch

git pull git://github.com/jonathanong/node-webp-bin.git

[jonathanong]

had trouble with using the compiled binary on Heroku. I just compile from source now and it works: https://github.com/funraiseme/webp

[shinnn]

You can use cwebp-bin instead.