Add GitHub Actions badge to README

Removes the old Travis badge and adds the GitHub Actions badge. Also
fixes the spelling of "DigitalOcean" in the README.

README.md

@@ -1,4 +1,4 @@
-# Goth: Multi-Provider Authentication for Go [![GoDoc](https://godoc.org/github.com/markbates/goth?status.svg)](https://godoc.org/github.com/markbates/goth) [![Build Status](https://travis-ci.org/markbates/goth.svg)](https://travis-ci.org/markbates/goth) [![Go Report Card](https://goreportcard.com/badge/github.com/markbates/goth)](https://goreportcard.com/report/github.com/markbates/goth)
+# Goth: Multi-Provider Authentication for Go [![GoDoc](https://godoc.org/github.com/markbates/goth?status.svg)](https://godoc.org/github.com/markbates/goth) [![Build Status](https://github.com/markbates/goth/workflows/ci/badge.svg)](https://github.com/markbates/goth/actions) [![Go Report Card](https://goreportcard.com/badge/github.com/markbates/goth)](https://goreportcard.com/report/github.com/markbates/goth)
 
 Package goth provides a simple, clean, and idiomatic way to write authentication
 packages for Go web applications.
@@ -26,7 +26,7 @@ $ go get github.com/markbates/goth
 * Cloud Foundry
 * Dailymotion
 * Deezer
-* Digital Ocean
+* DigitalOcean
 * Discord
 * Dropbox
 * Eve Online