add docs badge

Author: pfitzseb

README.md

@@ -1,6 +1,6 @@
 # Traceur
 
-[![Build Status](https://travis-ci.org/JunoLab/Traceur.jl.svg?branch=master)](https://travis-ci.org/JunoLab/Traceur.jl) 
+[![Build Status](https://travis-ci.org/JunoLab/Traceur.jl.svg?branch=master)](https://travis-ci.org/JunoLab/Traceur.jl) [![Docs](https://img.shields.io/badge/docs-latest-blue.svg)](https://JunoLab.github.io/Traceur.jl/latest)
 
 Traceur is essentially a codified version of the [Julia performance tips](https://docs.julialang.org/en/v1/manual/performance-tips/). You run your code, it tells you about any obvious performance traps.