Add version badge

Author: garyb

README.md

@@ -1,5 +1,6 @@
 # purescript-eff
 
+[![Latest release](http://img.shields.io/bower/v/purescript-eff.svg)](https://github.com/purescript/purescript-eff/releases)
 [![Build Status](https://travis-ci.org/purescript/purescript-eff.svg?branch=master)](https://travis-ci.org/purescript/purescript-eff)
 [![Dependency Status](https://www.versioneye.com/user/projects/55848cde3638610015000408/badge.svg?style=flat)](https://www.versioneye.com/user/projects/55848cde3638610015000408)