Fix the "dev" docs badge (#943)

Author: DilumAluthge

README.md

@@ -3,7 +3,7 @@
 [![Build Status](https://api.travis-ci.org/JuliaLang/IJulia.jl.svg)](https://travis-ci.org/JuliaLang/IJulia.jl)
 [![Build status](https://ci.appveyor.com/api/projects/status/aaw818ykpducu6ue?svg=true)](https://ci.appveyor.com/project/StevenGJohnson/ijulia-jl)
 [![](https://img.shields.io/badge/docs-stable-blue.svg)](https://JuliaLang.github.io/IJulia.jl/stable)
-[![](https://img.shields.io/badge/docs-latest-blue.svg)](https://JuliaLang.github.io/IJulia.jl/latest)
+[![](https://img.shields.io/badge/docs-latest-blue.svg)](https://JuliaLang.github.io/IJulia.jl/dev)
 
 
 # IJulia