Add js-emoji

The source repo iamcal/js-emoji uses submodules and does not have a structure that is cdn-friendly. I've forked it to generate a version that is, imho, more deployable on a cdn (minified, submodule files compiled, tagged, etc). The forked repo is at ping/js-emoji. 

update.json points to my forked repo that has releases tagged from a non-master branch (ping/js-emoji/tree/deploy-cdn/). Is this okay?