Fix codecov not displaying on GitHub

Author: eXpl0it3r

README.md

@@ -6,7 +6,7 @@
 
 [![Build status](https://ci.appveyor.com/api/projects/status/8jw2lq431kgg44jl/branch/master?svg=true)](https://ci.appveyor.com/project/sharwell/stylecopanalyzers/branch/master)
 
-[![codecov.io](http://codecov.io/github/DotNetAnalyzers/StyleCopAnalyzers/coverage.svg?branch=master)](http://codecov.io/github/DotNetAnalyzers/StyleCopAnalyzers?branch=master)
+[![codecov.io](https://codecov.io/github/DotNetAnalyzers/StyleCopAnalyzers/coverage.svg?branch=master)](https://codecov.io/github/DotNetAnalyzers/StyleCopAnalyzers?branch=master)
 
 This repository contains an implementation of the StyleCop rules using the .NET Compiler Platform. Where possible, code fixes are also provided to simplify the process of correcting violations.