Bump pngquant-bin

pngquant-bin 0.1.2 uses DOS line endings which causes errors on OS X when trying
to run it:

```
./node_modules/.../pngquant/node_modules/.bin/pngquant
env: node\r: No such file or directory
```
Merge pull request #3 from passy/patch-pngquant-bin

Bump pngquant-bin