Make VersionRange implement Comparable.

lib/src/version_constraint.dart

 // Copyright (c) 2014, 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.
 
 import 'patterns.dart';
 import 'version.dart';
 import 'version_range.dart';
 import 'version_union.dart';
 import 'utils.dart';
 
@@ skipping 176 matching lines @@
     }
 
     // Only allow Versions and VersionRanges here so we can more easily reason
     // about everything in [flattened]. _EmptyVersions and VersionUnions are
     // filtered out above.
     for (var constraint in flattened) {
       if (constraint is VersionRange) continue;
       throw new ArgumentError('Unknown VersionConstraint type $constraint.');
     }
 
-    flattened.sort(compareMax);
+    flattened.sort();
 
     var merged = <VersionRange>[];
     for (var constraint in flattened) {
       // Merge this constraint with the previous one, but only if they touch.
       if (merged.isEmpty ||
           (!merged.last.allowsAny(constraint) &&
               !areAdjacent(merged.last, constraint))) {
         merged.add(constraint);
       } else {
         merged[merged.length - 1] = merged.last.union(constraint);
@@ skipping 43 matching lines @@
   String toString() => '<empty>';
 }
 
 class _CompatibleWithVersionRange extends VersionRange {
   _CompatibleWithVersionRange(Version version) : super(
       min: version, includeMin: true,
       max: version.nextBreaking, includeMax: false);
 
   String toString() => '^$min';
 }