docs: add release version

README.md

 # Coca - toolbox for system refactoring and analysis
 
+![GitHub release (latest SemVer)](https://img.shields.io/github/v/release/phodal/coca)
 [![Build Status](https://travis-ci.org/phodal/coca.svg?branch=master)](https://travis-ci.org/phodal/coca)
 [![Maintainability](https://api.codeclimate.com/v1/badges/d5a5e060522403b1f79b/maintainability)](https://codeclimate.com/github/phodal/coca/maintainability)
 [![codecov](https://codecov.io/gh/phodal/coca/branch/master/graph/badge.svg)](https://codecov.io/gh/phodal/coca)