Auto-post links from #civictechnews that get X emoji reactions

This is totes just for kicks.

The idea is to automatically post a link to civictechto twitter when it gets a certain number of reaction emoji. So for example, auto-post link when it gets 5 thumbs-up

Could just use the link title as the Tweet content: https://github.com/sindresorhus/article-title

Related admin comment on social media strategy: (private)
https://civictechto.slack.com/archives/organize-the-things/p1464012511000088
### Resources
- https://github.com/18F/hubot-slack/blob/master/src/slack.coffee#L41
- https://github.com/slackhq/hubot-slack/pull/271
- https://github.com/18F/hubot-slack-github-issues/issues/10
- https://github.com/slackhq/hubot-slack/issues/251

Start by reading the linked src/slack.coffee entry point and the referenced hubot-slack resources. Clarify the reaction threshold and Twitter destination, then determine how the article-title utility fits the flow. Done means qualifying links from #civictechnews are automatically posted with their titles as tweet content.

Written by the indexing model from the issue text.