Add replacement for coin.coffee.

Author: sethjackson

replacements.json

@@ -4,6 +4,7 @@
   "asana.coffee": "https://github.com/hubot-scripts/hubot-asana",
   "ascii.coffee": "https://github.com/sanderploegsma/hubot-ascii-art",
   "auth": "https://github.com/hubot-scripts/hubot-auth",
+  "coin.coffee": "https://github.com/fordnox/hubot-coin",
   "darksky.coffee": "https://github.com/hubot-scripts/hubot-darksky",
   "factoids.coffee": "https://github.com/hubot-scripts/hubot-factoids",
   "gitlab.coffee": "https://github.com/spruce/hubot-gitlab-hooks",