Version 1.5.0

• Argument structs can define Description() and Epilogue(), which are added to the usage string

• Subcommands can have multiple aliases like this:

var args struct {
    Remove *struct{} `arg:"subcommand:remove|rm|r" help:"remove something from somewhere"`
}

• Improves formatting of usage string when the placeholder tag is set to empty string

• Do not handle --version when the args struct lacks a Version() function

• Add StructSubcommands to Config struct