Fix newly enforced lint (#193)

Author: kevmoo

test/command_parse_test.dart

@@ -2,8 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:test/test.dart';
 import 'package:args/args.dart';
+import 'package:test/test.dart';
+
 import 'test_utils.dart';
 
 void main() {

test/trailing_options_test.dart

@@ -2,8 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:test/test.dart';
 import 'package:args/args.dart';
+import 'package:test/test.dart';
 
 void main() {
   test('allowTrailingOptions defaults to true', () {