Add methods to Result. Bump version to 2.0 and remove deprecated features.

test/result/result_flattenAll_test.dart

+// Copyright (c) 2017, 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 "package:async/async.dart";
+import "package:test/test.dart";
+
+final someStack = StackTrace.current;
+Result<T> res<T>(T n) => new Result<T>.value(n);
+Result err(n) => new ErrorResult("$n", someStack);
+
+/// Helper function creating an iterable of results.
+Iterable<Result<int>> results(int count, {bool throwWhen(int index)}) sync* {
+  for (int i = 0; i < count; i++) {
+    if (throwWhen != null && throwWhen(i)) {
+      yield err(i);
+    } else {
+      yield res(i);
+    }
+  }
+}
+
+main() {
+  expectAll(result, expectation) {
+    if (expectation.isError) {
+      expect(result, expectation);
+    } else {
+      expect(result.isValue, true);
+      expect(result.asValue.value, expectation.asValue.value);
+    }
+  }
+
+  test("empty", () {
+    expectAll(Result.flattenAll<int>(results(0)), res([]));
+  });
+  test("single value", () {
+    expectAll(Result.flattenAll<int>(results(1)), res([0]));
+  });
+  test("single error", () {
+    expectAll(
+        Result.flattenAll<int>(results(1, throwWhen: (_) => true)), err(0));
+  });
+  test("multiple values", () {
+    expectAll(Result.flattenAll<int>(results(5)), res([0, 1, 2, 3, 4]));
+  });
+  test("multiple errors", () {
+    expectAll(Result.flattenAll<int>(results(5, throwWhen: (x) => x.isOdd)),
+        err(1)); // First error is result.
+  });
+  test("error last", () {
+    expectAll(
+        Result.flattenAll<int>(results(5, throwWhen: (x) => x == 4)), err(4));
+  });
+}