Add CodeTriage badge to opsdroid/opsdroid

Adds a badge showing the number of people helping this repo on CodeTriage.

[![Open Source Helpers](https://www.codetriage.com/opsdroid/opsdroid/badges/users.svg)](https://www.codetriage.com/opsdroid/opsdroid)

CodeTriage is an Open Source app that is designed to make contributing to Open Source projects easier. It works by sending subscribers a few open issues in their inbox. If subscribers get busy, there is an algorithm that backs off issue load so they do not get overwhelmed

[Read more about the CodeTriage project](https://www.codetriage.com/what).

Your project was picked by the human, @schneems. They selected it from the projects submitted to https://www.codetriage.com and hand edited the PR. How did your project get added to [CodeTriage](https://www.codetriage.com/what)? Roughly 5 months ago, [@jacobtomlinson](https://github.com/jacobtomlinson) added this project to CodeTriage in order to start contributing.

Adding a badge invites people to help contribute to your project. It also lets developers know that others are invested in the longterm success and maintainability of the project.

You can see an example of a CodeTriage badge on these popular OSS READMEs:

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While I am a bot, this PR was manually reviewed and monitored by a human - @schneems. My job is writing commit messages and handling PR logistics.

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Thanks for making your project Open Source! Any feedback is greatly appreciated.

README.md

@@ -1,6 +1,6 @@
  ![opsdroid](https://github.com/opsdroid/style-guidelines/raw/master/logos/logo-wide-light.png)[![Tweet](https://img.shields.io/twitter/url/http/shields.io.svg?style=social)](https://twitter.com/intent/tweet?text=Check%20out%20opsdroid,%20an%20awesome%20open%20source%20chatbot%20framework%20written%20in%20Python.&url=https://opsdroid.github.io/&via=opsdroid&hashtags=chatbots,chatops,devops,automation,opensource)
 
-[![Current version of pypi](https://img.shields.io/pypi/v/opsdroid.svg)](https://pypi.python.org/pypi) [![Build Status](https://travis-ci.org/opsdroid/opsdroid.svg?branch=release)](https://travis-ci.org/opsdroid/opsdroid) [![Build status](https://ci.appveyor.com/api/projects/status/9qodmi74r234x4cv/branch/master?svg=true)](https://ci.appveyor.com/project/jacobtomlinson/opsdroid/branch/master) [![codecov](https://codecov.io/gh/opsdroid/opsdroid/branch/master/graph/badge.svg)](https://codecov.io/gh/opsdroid/opsdroid) [![Updates](https://pyup.io/repos/github/opsdroid/opsdroid/shield.svg)](https://pyup.io/repos/github/opsdroid/opsdroid/) [![Dependency Status](https://dependencyci.com/github/opsdroid/opsdroid/badge)](https://dependencyci.com/github/opsdroid/opsdroid) [![Docker Image](https://img.shields.io/badge/docker-ready-blue.svg)](https://hub.docker.com/r/opsdroid/opsdroid/) [![Docker Layers](https://images.microbadger.com/badges/image/opsdroid/opsdroid.svg)](https://microbadger.com/#/images/opsdroid/opsdroid) [![Documentation Status](https://readthedocs.org/projects/opsdroid/badge/?version=stable)](http://opsdroid.readthedocs.io/en/stable/?badge=stable) [![Gitter Badge](https://img.shields.io/badge/gitter-join%20chat-4fb896.svg)](https://gitter.im/opsdroid) [![Backers on Open Collective](https://opencollective.com/opsdroid/backers/badge.svg)](#backers) [![Sponsors on Open Collective](https://opencollective.com/opsdroid/sponsors/badge.svg)](#sponsors) 
+[![Current version of pypi](https://img.shields.io/pypi/v/opsdroid.svg)](https://pypi.python.org/pypi) [![Build Status](https://travis-ci.org/opsdroid/opsdroid.svg?branch=release)](https://travis-ci.org/opsdroid/opsdroid) [![Build status](https://ci.appveyor.com/api/projects/status/9qodmi74r234x4cv/branch/master?svg=true)](https://ci.appveyor.com/project/jacobtomlinson/opsdroid/branch/master) [![codecov](https://codecov.io/gh/opsdroid/opsdroid/branch/master/graph/badge.svg)](https://codecov.io/gh/opsdroid/opsdroid) [![Updates](https://pyup.io/repos/github/opsdroid/opsdroid/shield.svg)](https://pyup.io/repos/github/opsdroid/opsdroid/) [![Dependency Status](https://dependencyci.com/github/opsdroid/opsdroid/badge)](https://dependencyci.com/github/opsdroid/opsdroid) [![Docker Image](https://img.shields.io/badge/docker-ready-blue.svg)](https://hub.docker.com/r/opsdroid/opsdroid/) [![Docker Layers](https://images.microbadger.com/badges/image/opsdroid/opsdroid.svg)](https://microbadger.com/#/images/opsdroid/opsdroid) [![Documentation Status](https://readthedocs.org/projects/opsdroid/badge/?version=stable)](http://opsdroid.readthedocs.io/en/stable/?badge=stable) [![Gitter Badge](https://img.shields.io/badge/gitter-join%20chat-4fb896.svg)](https://gitter.im/opsdroid) [![Backers on Open Collective](https://opencollective.com/opsdroid/backers/badge.svg)](#backers) [![Sponsors on Open Collective](https://opencollective.com/opsdroid/sponsors/badge.svg)](#sponsors) [![Open Source Helpers](https://www.codetriage.com/opsdroid/opsdroid/badges/users.svg)](https://www.codetriage.com/opsdroid/opsdroid)
 
 An open source chat bot framework written in python. It is designed to be extendable, scalable and simple.