CircleCI now support nice (with shields.io) badges.

Because of the new Heroku pricing circleci-badges.herokuapp.com has been shut down, please update your badge links.

So please replace:

https://circleci-badges.herokuapp.com/:owner/:repo/:circle-ci-badge-token

by:

https://circleci.com/gh/:owner>/:repo.svg?style=shield&circle-token=:circle-ci-badge-token