All listed continuous integration providers offer free plans for open source repositories.

1) Using travis

1. Add a .travis.yml

language: node_js
node_js:
  - "0.12"
  - iojs

1. Add your project on Travis (flip the button to on - this will create a github webhook)

With the travis.yml you can configure even more!

2) Using circleci

1. add a project
2. Choose the correct owner/org and repo
3. Click on build project

You might want to save same artifacts or configure more details in a circle.yml

3) Using drone.io

• new project -> github -> add your project
• choose node
• setup build script

npm install --silent
npm test
npm run build

• change the nvm to node 0.10
• artifacts: enter the relative dir of files that should be downloadable (e.g. build/biojs_io_fasta.min.js)

5) Add other badges

There are plenty of fancy badges, here is a list to have a quick start.

[![NPM version](http://img.shields.io/npm/v/<package-name>.svg)](https://www.npmjs.org/package/<package-name>)
[![Dependencies](https://david-dm.org/<username>/<package-name>.png)](https://david-dm.org/greenify/<package-name>)
[![Code Climate](https://codeclimate.com/github/<username>/<package-name>/badges/gpa.svg)](https://codeclimate.com/github/<username>/<package-name>)
[![NPM downloads](http://img.shields.io/npm/dm/<package-name>.svg)](https://www.npmjs.org/package/<package-name>)