Add parameter to status_s.png in attempt to force override github's cache

README.md

 # CodeMirror
 [![Build Status](https://travis-ci.org/codemirror/CodeMirror.svg)](https://travis-ci.org/codemirror/CodeMirror)
 [![NPM version](https://img.shields.io/npm/v/codemirror.svg)](https://www.npmjs.org/package/codemirror)  
-[Funding status: ![maintainer happiness](https://marijnhaverbeke.nl/fund/status_s.png)](https://marijnhaverbeke.nl/fund/)
+[Funding status: ![maintainer happiness](https://marijnhaverbeke.nl/fund/status_s.png?again)](https://marijnhaverbeke.nl/fund/)
 
 CodeMirror is a JavaScript component that provides a code editor in
 the browser. When a mode is available for the language you are coding