Add Snowplow Maintenance Badge (close snowplow#820)

Author: Paul Boocock

README.md

@@ -1,5 +1,6 @@
 # JavaScript web analytics for Snowplow
 
+[![actively-maintained]][tracker-classificiation]
 [![Build Status][travis-image]][travis]
 [![Selenium Test Status][saucelabs-button-image]][saucelabs]
 [![Code Climate][codeclimate-image]][codeclimate]
@@ -16,19 +17,18 @@ client-side tier of your websites and web apps.
 
 ## Find out more
 
-| Technical Docs                      | Setup Guide                  | Roadmap & Contributing               |         
+| Technical Docs                      | Setup Guide                  | Roadmap & Contributing               |
 |-------------------------------------|------------------------------|--------------------------------------|
-| [![i1][techdocs-image]][tech-docs] | [ ![i2][setup-image]][setup] | ![i3][roadmap-image]                 |
+| [![i1][techdocs-image]][tech-docs] | [![i2][setup-image]][setup] | ![i3][roadmap-image]                 |
 | [Technical Docs][tech-docs]         | [Setup Guide][setup]         | _coming soon_                        |
 
-
 ## Developers
 
 ### Contributing quickstart
 
 Assuming git and [Docker][docker-install] installed:
 
-```
+```bash
  host$ git clone https://github.com/snowplow/snowplow-javascript-tracker.git
  host$ cd snowplow-javascript-tracker
  host$ docker build -t tracker .
@@ -75,12 +75,14 @@ Licensed under the [Simplified BSD][bsd] license.
 [setup-image]: https://d3i6fms1cm1j0i.cloudfront.net/github/images/setup.png
 [roadmap-image]: https://d3i6fms1cm1j0i.cloudfront.net/github/images/roadmap.png
 [grunt-image]: https://cdn.gruntjs.com/builtwith.png
-[grunt]: http://gruntjs.com/
+[grunt]: https://gruntjs.com/
 [travis-image]: https://travis-ci.org/snowplow/snowplow-javascript-tracker.png?branch=master
 [travis]: http://travis-ci.org/snowplow/snowplow-javascript-tracker
 [codeclimate-image]: https://codeclimate.com/github/snowplow/snowplow-javascript-tracker.png
-[codeclimate]: https://codeclimate.com/github/snowplow/snowplow-javascript-tracker      
+[codeclimate]: https://codeclimate.com/github/snowplow/snowplow-javascript-tracker
 [saucelabs]: https://saucelabs.com/u/snowplow
 [saucelabs-button-image]: https://saucelabs.com/buildstatus/snowplow
 [saucelabs-matrix-image]: https://saucelabs.com/browser-matrix/snowplow.svg
 [license-image]: http://img.shields.io/badge/license-simplified--bsd-blue.svg?style=flat
+[tracker-classificiation]: https://github.com/snowplow/snowplow/wiki/Tracker-Maintenance-Classification
+[actively-maintained]: https://img.shields.io/static/v1?style=flat&label=Snowplow&message=Actively%20Maintained&color=6638b8&labelColor=9ba0aa&logo=data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAMAAAAoLQ9TAAAAeFBMVEVMaXGXANeYANeXANZbAJmXANeUANSQAM+XANeMAMpaAJhZAJeZANiXANaXANaOAM2WANVnAKWXANZ9ALtmAKVaAJmXANZaAJlXAJZdAJxaAJlZAJdbAJlbAJmQAM+UANKZANhhAJ+EAL+BAL9oAKZnAKVjAKF1ALNBd8J1AAAAKHRSTlMAa1hWXyteBTQJIEwRgUh2JjJon21wcBgNfmc+JlOBQjwezWF2l5dXzkW3/wAAAHpJREFUeNokhQOCA1EAxTL85hi7dXv/E5YPCYBq5DeN4pcqV1XbtW/xTVMIMAZE0cBHEaZhBmIQwCFofeprPUHqjmD/+7peztd62dWQRkvrQayXkn01f/gWp2CrxfjY7rcZ5V7DEMDQgmEozFpZqLUYDsNwOqbnMLwPAJEwCopZxKttAAAAAElFTkSuQmCC