Update badges

- Link to new [Spectrum community forum](https://spectrum.chat/styled-components)
- Remove build status badges (they aren't necessary at all since they don't correspond to what people install)
- Remove "Supported by Thinkmill"-badge (I no longer work there)

README.md

@@ -10,10 +10,7 @@ npm install --save styled-components
 ```
 
 [![npm](https://img.shields.io/npm/v/styled-components.svg)](https://www.npmjs.com/package/styled-components)
-[![Travis Build Status](https://travis-ci.org/styled-components/styled-components.svg?branch=master)](https://travis-ci.org/styled-components/styled-components)
-[![AppVeyor Build Status](https://ci.appveyor.com/api/projects/status/github/gruntjs/grunt?branch=master&svg=true)](https://ci.appveyor.com/project/mxstbr/styled-components)
-[![Supported by Thinkmill](https://thinkmill.github.io/badge/heart.svg)](http://thinkmill.com.au/?utm_source=github&utm_medium=badge&utm_campaign=styled-components)
-[![gitter](https://camo.githubusercontent.com/54dc79dc7da6b76b17bc8013342da9b4266d993c/68747470733a2f2f6261646765732e6769747465722e696d2f6d78737462722f72656163742d626f696c6572706c6174652e737667)](https://gitter.im/styled-components/styled-components)
+[![Join the community on Spectrum](https://withspectrum.github.io/badge/badge.svg)](https://spectrum.chat/styled-components)
 
 ![gzip size](http://img.badgesize.io/https://unpkg.com/styled-components/dist/styled-components.min.js?compression=gzip&label=gzip%20size)
 ![size](http://img.badgesize.io/https://unpkg.com/styled-components/dist/styled-components.min.js?label=size)