docs: Update CI badge

... and remove old Travis CI config

README.md

@@ -1,8 +1,9 @@
-[![Build Status](https://travis-ci.com/bmaupin/go-epub.svg?branch=master)](https://travis-ci.com/bmaupin/go-epub)
+[![CI](https://github.com/bmaupin/go-epub/workflows/CI/badge.svg)](https://github.com/bmaupin/go-epub/actions)
 [![Coverage Status](https://coveralls.io/repos/github/bmaupin/go-epub/badge.svg?branch=master)](https://coveralls.io/github/bmaupin/go-epub?branch=master)
 [![Go Report Card](https://goreportcard.com/badge/github.com/bmaupin/go-epub)](https://goreportcard.com/report/github.com/bmaupin/go-epub)
 [![License](https://img.shields.io/badge/license-MIT-blue.svg)](https://github.com/bmaupin/go-epub/blob/master/LICENSE)
 [![GoDoc](https://godoc.org/github.com/bmaupin/go-epub?status.svg)](https://godoc.org/github.com/bmaupin/go-epub)
+
 ---
 
 ### Features