Merge pull request flutter#125 from dart-lang/opt_news

doc cleanup: - optional `new`s

Author: pq

lib/src/custom_matcher.dart

@@ -28,7 +28,7 @@ import 'util.dart';
 /// and then use this for example like:
 ///
 /// ```dart
-/// expect(inventoryItem, new HasPrice(greaterThan(0)));
+/// expect(inventoryItem, HasPrice(greaterThan(0)));
 /// ```
 class CustomMatcher extends Matcher {
   final String _featureDescription;

lib/src/type_matcher.dart

@@ -19,15 +19,15 @@ TypeMatcher<T> isA<T>() => TypeMatcher<T>();
 /// object.
 ///
 /// ```dart
-/// expect(shouldBeDuration, new TypeMatcher<Duration>());
+/// expect(shouldBeDuration, TypeMatcher<Duration>());
 /// ```
 ///
 /// If you want to further validate attributes of the specified [Type], use the
 /// [having] function.
 ///
 /// ```dart
 /// void shouldThrowRangeError(int value) {
-///   throw new RangeError.range(value, 10, 20);
+///   throw RangeError.range(value, 10, 20);
 /// }
 ///
 /// expect(