Grunt publish

This updates how we use Grunt a bit (includes updated docs), so that we no longer bundle Grunt and its dependencies for NPM users. Pre-compiled (and minified) assets will now ship with the npm module by default.

If you do install devDependencies with the repo, you can continue using `grunt dev`. To deploy directly from this repo, however, you'll need to remove public/ from your .gitignore.

This brings `npm install buckets` down from over a minute (and still requiring assets to be built), to under 20 seconds (w/precompiled assets). Most notably, the previous "Deploy to Heroku" button which could take over 10 minutes, now takes under a minute.