Cleaned up exported func comments per golint

category.go

@@ -1,7 +1,9 @@
 package cli
 
+// CommandCategories is a slice of *CommandCategory.
 type CommandCategories []*CommandCategory
 
+// CommandCategory is a category containing commands.
 type CommandCategory struct {
 	Name     string
 	Commands Commands
@@ -19,6 +21,7 @@ func (c CommandCategories) Swap(i, j int) {
 	c[i], c[j] = c[j], c[i]
 }
 
+// AddCommand adds a command to a category.
 func (c CommandCategories) AddCommand(category string, command Command) CommandCategories {
 	for _, commandCategory := range c {
 		if commandCategory.Name == category {