Add free badges for the project (#4)

- Badges for release, build passing, license and docs
 - TODO add badge for coverage

README.rst → README.md

@@ -1,5 +1,10 @@
 Common Go Tools
 =====================
+[![Current Release](https://img.shields.io/github/release/flytestdlib.svg)](https://github.com/lyft/flytestdlib/releases/latest)
+[![Build Status](https://travis-ci.org/lyft/flytestdlib.svg?branch=master)](https://travis-ci.org/lyft/flytestdlib)
+[![GoDoc](https://godoc.org/github.com/lyft/flytestdlib?status.svg)](https://godoc.org/github.com/lyft/flytestdlib)
+[![License](https://img.shields.io/badge/LICENSE-Apache2.0-ff69b4.svg)](http://www.apache.org/licenses/LICENSE-2.0.html)
+
 Shared components we found ourselves building time and time again, so we collected them in one place!
 
 This library consists of: