Added spectrum community (#440)

Such a great project deserve a community.

README.md

@@ -7,6 +7,7 @@
 [![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg)](http://makeapullrequest.com)
 [![MIT License](https://img.shields.io/github/license/dawnlabs/carbon.svg)](https://github.com/dawnlabs/carbon/blob/master/LICENSE)
 [![Greenkeeper badge](https://badges.greenkeeper.io/dawnlabs/carbon.svg)](https://greenkeeper.io/)
+[![Join the community on Spectrum](https://withspectrum.github.io/badge/badge.svg)](https://spectrum.chat/carbon-now)
 <br></br>
 [![Deploy to now](https://deploy.now.sh/static/button.svg)](https://deploy.now.sh/?repo=https://github.com/dawnlabs/carbon&env=TWITTER_CONSUMER_KEY&env=TWITTER_CONSUMER_SECRET&env=TWITTER_ACCESS_TOKEN_KEY&env=TWITTER_ACCESS_TOKEN_SECRET&env=LOGS_SECRET_PREFIX)