Adding Matt Bradley's livestamp add-on for moment.js

Requesting to add livestamp to the repo.  It is an addon for moment.js that provides timeago.js-like functionality but without the bugs of timeago.  It has 151 github stars and the source came from the listed production-ready version here: http://mattbradley.github.io/livestampjs/

npm test returns the warning about no readme.md but otherwise is good.

Thanks!