[README.md] add Codacy badge

Author: chrissimpkins

README.md

@@ -3,5 +3,5 @@
 [![Build Status](https://travis-ci.org/source-foundry/fdiff.svg?branch=master)](https://travis-ci.org/source-foundry/fdiff)
 [![Build status](https://ci.appveyor.com/api/projects/status/eafvbkc4iyv78dip/branch/master?svg=true)](https://ci.appveyor.com/project/chrissimpkins/fdiff/branch/master)
 [![codecov](https://codecov.io/gh/source-foundry/fdiff/branch/master/graph/badge.svg)](https://codecov.io/gh/source-foundry/fdiff)
-
+[![Codacy Badge](https://api.codacy.com/project/badge/Grade/b58954eda44b4fd88ad8f4fa06e8010b)](https://www.codacy.com/app/SourceFoundry/fdiff)