added alfred app workflow reference

I developmed an Alfred app Workflow to wrap around your ImageOptim-CLI implementation. It's working pretty good within me and my co-workers. I'm adding the link to it in your readme file

BTW, I modified your library in my Workflow to use ImageMagick's mogrify to compress JPGs with a standard 75 quality if JPEGmini is unavailable, if you're interested I can push it in my fork and do a PR

Cheers