Add notes on usage as a library

README.md

@@ -1,7 +1,7 @@
 # kepubify
-[![Build Status](https://travis-ci.org/geek1011/kepubify.svg?branch=master)](https://travis-ci.org/geek1011/kepubify) [![Go Report Card](https://goreportcard.com/badge/github.com/geek1011/kepubify)](https://goreportcard.com/report/github.com/geek1011/kepubify)
+[![Build Status](https://travis-ci.org/geek1011/kepubify.svg?branch=master)](https://travis-ci.org/geek1011/kepubify) [![Go Report Card](https://goreportcard.com/badge/github.com/geek1011/kepubify)](https://goreportcard.com/report/github.com/geek1011/kepubify) [![GoDoc Reference](https://img.shields.io/badge/godoc-reference-blue.svg)](https://godoc.org/github.com/geek1011/kepubify/kepub)
 
-Convert your ePubs into kepubs, with a easy-to-use command-line tool.
+Convert your ePubs into kepubs, with an easy-to-use tool. Kepubify can also be embedded i to your own apps with the import path `github.com/geek1011/kepubify/kepub`.
 
 ## Usage
 - On Windows, you can drag your book on top of `kepubify.exe`