Combine unmodifiable_collection package into collection_helpers.

pkg/args/lib/args.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 /**
  * Parser support for transforming raw command-line arguments into a set
  * of options and values.
  *
  * This library supports [GNU][] and [POSIX][] style options, and it works
  * in both server-side and client-side apps.
@@ skipping 222 matching lines @@
  *
  *     parser.addOption('arch', help: 'The architecture to compile for',
  *         allowedHelp: {
  *           'ia32': 'Intel x86',
  *           'arm': 'ARM Holding 32-bit chip'
  *         });
  *
  * To display the help, use the ArgParser getUsage() method:
  *
  *     print(parser.getUsage());
- * 
+ *
  * The resulting string looks something like this:
  *
  *     --mode            The compiler configuration
  *                       [debug, release]
  *
  *     --[no-]verbose    Show additional diagnostic info
  *     --arch            The architecture to compile for
  *
  *           [arm]       ARM Holding 32-bit chip
  *           [ia32]      Intel x86
  *
  * To assist the formatting of the usage help, single-line help text is
  * followed by a single new line. Options with multi-line help text are
  * followed by two new lines. This provides spatial diversity between options.
  *
  * [posix]: http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap12.html#tag_12_02
  * [gnu]: http://www.gnu.org/prep/standards/standards.html#Command_002dLine-Interfaces
  */
 library args;
 
-import 'package:unmodifiable_collection/unmodifiable_collection.dart';
+import 'package:collection_helpers/wrappers.dart';
 
 import 'src/parser.dart';
 import 'src/usage.dart';
 import 'src/options.dart';
 export 'src/options.dart';
 
 /**
  * A class for taking a list of raw command line arguments and parsing out
  * options and flags from them.
  */
@@ skipping 171 matching lines @@
           'Could not find an option named "$name".');
     }
 
     return _options[name];
   }
 
   /** Get the names of the options as an [Iterable]. */
   Iterable<String> get options => _options.keys;
 }