Add a README for the i18n middleware (#960)

* Add a README for the i18n middleware

* Remove bad indentation

middleware/i18n/README.md

@@ -0,0 +1,41 @@
+i18n middleware
+===============
+
+This Buffalo middleware enables i18n features in your app:
+* User language detection from configurable sources
+* Translation helper using locales bundles from github.com/nicksnyder/go-i18n
+* Localized views
+
+Installation
+------------
+
+This middleware is setup by default on a new Buffalo app:
+
+**actions/app.go**
+```go
+var app *buffalo.App
+
+// T is used to provide translations
+var T *i18n.Translator
+
+// App is where all routes and middleware for buffalo
+// should be defined. This is the nerve center of your
+// application.
+func App() *buffalo.App {
+    if app == nil {
+        // [...]
+
+        // Setup and use translations:
+	var err error
+	if T, err = i18n.New(packr.NewBox("../locales"), "en"); err != nil {
+		app.Stop(err)
+	}
+	app.Use(T.Middleware())
+    }
+    return app
+}
+```
+
+Use `i18n.New` to create a new instance of the translation module, then add the middleware (`T.Middleware()`) to the app to enable its features.
+
+See https://gobuffalo.io/docs/localization for further info about Buffalo translation features and configuration.