Adding GoDoc button

README.md

@@ -1,7 +1,7 @@
 email
 =====
 
-[![Build Status](https://travis-ci.org/jordan-wright/email.png?branch=master)](https://travis-ci.org/jordan-wright/email)
+[![Build Status](https://travis-ci.org/jordan-wright/email.png?branch=master)](https://travis-ci.org/jordan-wright/email) [![GoDoc](https://godoc.org/github.com/jordan-wright/email?status.svg)](https://godoc.org/github.com/jordan-wright/email)
 
 Robust and flexible email library for Go