use alternate badge URLs instead of img.shields.io

Author: eddelbuettel

ChangeLog

@@ -1,3 +1,7 @@
+2017-06-07  Dirk Eddelbuettel  <edd@debian.org>
+
+	* README.md: Use alternates for img.shields.io GPL-2+ badges
+
 2017-06-06  Yu Gong  <armgong@yahoo.com>
 
         * src/api.cpp: Also permit compilation under Haiku-OS

README.md

@@ -1,4 +1,4 @@
-## Rcpp [![Build Status](https://travis-ci.org/RcppCore/Rcpp.svg)](https://travis-ci.org/RcppCore/Rcpp) [![License](http://img.shields.io/badge/license-GPL%20%28%3E=%202%29-brightgreen.svg?style=flat)](http://www.gnu.org/licenses/gpl-2.0.html) [![CRAN](http://www.r-pkg.org/badges/version/Rcpp)](https://cran.r-project.org/package=Rcpp) [![Downloads](http://cranlogs.r-pkg.org/badges/Rcpp?color=brightgreen)](http://www.r-pkg.org/pkg/Rcpp) [![Coverage Status](https://img.shields.io/codecov/c/github/RcppCore/Rcpp/master.svg)](https://codecov.io/github/RcppCore/Rcpp?branch=master)
+## Rcpp [![Build Status](https://travis-ci.org/RcppCore/Rcpp.svg)](https://travis-ci.org/RcppCore/Rcpp) [![License](https://eddelbuettel.github.io/badges/GPL2+.svg)](http://www.gnu.org/licenses/gpl-2.0.html) [![CRAN](http://www.r-pkg.org/badges/version/Rcpp)](https://cran.r-project.org/package=Rcpp) [![Downloads](http://cranlogs.r-pkg.org/badges/Rcpp?color=brightgreen)](http://www.r-pkg.org/pkg/Rcpp) [![Coverage Status](https://codecov.io/gh/RcppCore/Rcpp/graph/badge.svg)](https://codecov.io/github/RcppCore/Rcpp?branch=master)
 
 ### Seamless R and C++ Integration