Remove accents in URLs

So the taxonomy `Gérard Depardieu` gives paths on the form `gerard-depardieu`.

Unfortunately this introduces two imports from the `golang.org/`, but Unicode-normalization isn't something we'd want to write from scratch.

See https://blog.golang.org/normalization

See #1180

helpers/path.go

@@ -19,6 +19,8 @@ import (
 	"github.com/spf13/afero"
 	jww "github.com/spf13/jwalterweatherman"
 	"github.com/spf13/viper"
+	"golang.org/x/text/transform"
+	"golang.org/x/text/unicode/norm"
 	"io"
 	"os"
 	"path/filepath"
@@ -97,9 +99,18 @@ func UnicodeSanitize(s string) string {
 		}
 	}
 
+	// remove accents - see https://blog.golang.org/normalization
+	t := transform.Chain(norm.NFD, transform.RemoveFunc(isMn), norm.NFC)
+	result, _, _ := transform.String(t, string(target))
+	return result
+
 	return string(target)
 }
 
+func isMn(r rune) bool {
+	return unicode.Is(unicode.Mn, r) // Mn: nonspacing marks
+}
+
 // ReplaceExtension takes a path and an extension, strips the old extension
 // and returns the path with the new extension.
 func ReplaceExtension(path string, newExt string) string {