remove AppVeyor (doesn't exist) and fix links

Author: visr

README.md

@@ -1,7 +1,6 @@
 
-[![Build Status](https://api.travis-ci.org/JuliaGeometry/GeometryBasics.jl.svg?branch=master)](https://travis-ci.com/SimonDanisch/GeometryBasics.jl)
-[![Build Status](https://ci.appveyor.com/api/projects/status/github/SimonDanisch/GeometryBasics.jl?svg=true)](https://ci.appveyor.com/project/SimonDanisch/GeometryBasics-jl)
-[![Codecov](https://codecov.io/gh/JuliaGeometry/GeometryBasics.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/SimonDanisch/GeometryBasics.jl)
+[![Build Status](https://api.travis-ci.org/JuliaGeometry/GeometryBasics.jl.svg?branch=master)](https://travis-ci.com/JuliaGeometry/GeometryBasics.jl)
+[![Codecov](https://codecov.io/gh/JuliaGeometry/GeometryBasics.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/JuliaGeometry/GeometryBasics.jl)
 
 **Documentation**:
 [![Docs - stable](https://img.shields.io/badge/docs-stable-lightgrey.svg)](http://juliageometry.github.io/GeometryBasics.jl/stable/)