Revert "Remove Expect from core library."

pkg/yaml/test/yaml_test.dart

 // Copyright (c) 2012, 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.
 
 library yaml_test;
 
-// TODO(rnystrom): rewrite tests so that they don't need "Expect".
-import "package:expect/expect.dart";
 import 'package:unittest/unittest.dart';
 import 'package:yaml/yaml.dart';
 import 'package:yaml/deep_equals.dart';
 // TODO(jmesserly): we should not be reaching outside the YAML package
 // The http package has a similar problem.
 import '../../../tests/utils/test_utils.dart';
 
 /// Constructs a new yaml.YamlMap, optionally from a normal Map.
 Map yamlMap([Map from]) =>
     from == null ? new YamlMap() : new YamlMap.from(from);
@@ skipping 1853 matching lines @@
         A null: null
         Also a null: # Empty
         Not a null: ""
         Booleans: [ true, True, false, FALSE ]
         Integers: [ 0, 0o7, 0x3A, -19 ]
         Floats: [ 0., -0.0, .5, +12e03, -2E+05 ]
         Also floats: [ .inf, -.Inf, +.INF, .NAN ]''');
     });
   });
 }