Remove CategorizedHelp from App and allow subcommands to have categories

Just place all subcommands in categories, the default category will be
"" which will properly format the output (and group commands that have
no category).

Also allow subcommands to have categories.

Lastly, augment the test to check the output.

app.go

@@ -35,8 +35,6 @@ type App struct {
 	HideHelp bool
 	// Boolean to hide built-in version flag
 	HideVersion bool
-	// Display commands by category
-	CategorizedHelp bool
 	// Populate on app startup, only gettable throught method Categories()
 	categories CommandCategories
 	// An action to execute when the bash-completion flag is set
@@ -100,14 +98,6 @@ func (a *App) Run(arguments []string) (err error) {
 		a.Authors = append(a.Authors, Author{Name: a.Author, Email: a.Email})
 	}
 
-	if a.CategorizedHelp {
-		a.categories = CommandCategories{}
-		for _, command := range a.Commands {
-			a.categories = a.categories.AddCommand(command.Category, command)
-		}
-	}
-	sort.Sort(a.categories)
-
 	newCmds := []Command{}
 	for _, c := range a.Commands {
 		if c.HelpName == "" {
@@ -117,6 +107,12 @@ func (a *App) Run(arguments []string) (err error) {
 	}
 	a.Commands = newCmds
 
+	a.categories = CommandCategories{}
+	for _, command := range a.Commands {
+		a.categories = a.categories.AddCommand(command.Category, command)
+	}
+	sort.Sort(a.categories)
+
 	// append help to commands
 	if a.Command(helpCommand.Name) == nil && !a.HideHelp {
 		a.Commands = append(a.Commands, helpCommand)