Added license badge.

Author: gslowikowski

README.md

@@ -8,6 +8,7 @@ google group for help, bug reports, feature requests, and general
 discussion on scoverage.
 
 [![Build Status](https://travis-ci.org/scoverage/sbt-scoverage.png?branch=master)](https://travis-ci.org/scoverage/sbt-scoverage)
+[![License](http://img.shields.io/:license-Apache%202-red.svg)](http://www.apache.org/licenses/LICENSE-2.0.txt)
 
 ## How to use