Add badge

Author: nicolasstucki

README.md

@@ -2,6 +2,7 @@
 
 [![Install extension](https://img.shields.io/badge/scala-vscode-blue.png)](vscode:extension/scala-lang.scala)
 [![Version](https://img.shields.io/github/package-json/v/scala/vscode-scala-syntax.svg)](https://marketplace.visualstudio.com/items?itemName=scala-lang.scala)
+[![Build Status](https://travis-ci.org/scala/vscode-scala-syntax.svg?branch=master)](https://travis-ci.org/scala/vscode-scala-syntax)
 
 Visual Studio Code extension providing syntax highlighting for Scala source
 files.