pkg/matcher: add isNaN and isNotNaN matchers

pkg/intl/test/number_format_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 number_format_test;
 
 import 'package:unittest/unittest.dart';
 import 'package:intl/number_symbols_data.dart';
@@ skipping 101 matching lines @@
 
   test('Simple set of numbers', () {
     var number = new NumberFormat();
     for (var x in allTestNumbers.keys) {
       var formatted = number.format(allTestNumbers[x]);
       expect(formatted, x);
       if (!testNumbersWeCannotReadBack.containsKey(x)) {
         var readBack = number.parse(formatted);
         // Even among ones we can read back, we can't test NaN for equality.
         if (allTestNumbers[x].isNaN) {
-          expect(readBack.isNaN, isTrue);
+          expect(readBack, isNaN);
         } else {
           expect(readBack, allTestNumbers[x]);
         }
       }
     }
   });
 
   test('Exponential form', () {
     var number = new NumberFormat("#.###E0");
     for (var x in testExponential.keys) {
@@ skipping 36 matching lines @@
   });
 
   test('Unparseable', () {
     var format = new NumberFormat.currencyPattern();
     expect(() => format.parse("abcdefg"), throwsFormatException);
     expect(() => format.parse(""), throwsFormatException);
     expect(() => format.parse("1.0zzz"), throwsFormatException);
     expect(() => format.parse("-∞+1"), throwsFormatException);
   });
 }