Document that Command.argParser can be overridden. (#72)
See #68
diff --git a/lib/command_runner.dart b/lib/command_runner.dart
index 2fe1517..13b0a6e 100644
--- a/lib/command_runner.dart
+++ b/lib/command_runner.dart
@@ -267,6 +267,9 @@
/// the constructor); they'll end up available via [argResults]. Subcommands
/// should be registered with [addSubcommand] rather than directly on the
/// parser.
+ ///
+ /// This can be overridden to change the arguments passed to the `ArgParser`
+ /// constructor.
ArgParser get argParser => _argParser;
final _argParser = new ArgParser();