Update README.md

Author: manthey

README.md

@@ -2,7 +2,7 @@
 
 [![Build Status](https://travis-ci.com/OpenGeoscience/geojs.svg?branch=master)](https://travis-ci.com/OpenGeoscience/geojs)
 [![codecov.io](https://codecov.io/github/OpenGeoscience/geojs/coverage.svg?branch=master)](https://codecov.io/github/OpenGeoscience/geojs?branch=master)
-[![DOI](https://zenodo.org/badge/doi/10.5281/zenodo.15459.svg)](https://dx.doi.org/10.5281/zenodo.15459)
+[![DOI](https://img.shields.io/badge/DOI-10.5281%2Fzenodo.15459-blue)](https://dx.doi.org/10.5281/zenodo.15459)
 [![Gitter](https://badges.gitter.im/OpenGeoscience/geojs.svg)](https://gitter.im/OpenGeoscience/geojs?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
 
 GeoJS is intended to bridge the gap between