app: Fix trailing space for Author.String()

This code initially landed with lots of space:

  '{name}  <{email}> '

or:

  '{name} '

in 3d718330 (app, help: add support for multiple authors, 2015-01-31).
The doubled space between the name and email was removed in c6592bb4
(app, help: add backwards compatibility for Authors, 2015-02-21), but
a trailing space remained in both the email and email-less cases.
This commit removes that trailing space.

app.go

@@ -458,10 +458,10 @@ type Author struct {
 func (a Author) String() string {
 	e := ""
 	if a.Email != "" {
-		e = "<" + a.Email + "> "
+		e = " <" + a.Email + ">"
 	}
 
-	return fmt.Sprintf("%v %v", a.Name, e)
+	return fmt.Sprintf("%v%v", a.Name, e)
 }
 
 // HandleAction uses ✧✧✧reflection✧✧✧ to figure out if the given Action is an