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

lib/src/result/future.dart

Index: lib/src/result/future.dart
diff --git a/lib/src/result/future.dart b/lib/src/result/future.dart
index 749b101f0678210e1c5316d1cf0b405549741858..6a4cc99d1717af4de38693a1f6b6a5c663efcbbf 100644
--- a/lib/src/result/future.dart
+++ b/lib/src/result/future.dart
@@ -19,15 +19,9 @@ class ResultFuture<T> extends DelegatingFuture<T> {
   Result<T> get result => _result;
   Result<T> _result;
 
-  factory ResultFuture(Future<T> future) {
-    ResultFuture<T> resultFuture;
-    resultFuture = new ResultFuture._(() async {
-      var result = await Result.capture(future);
-      resultFuture._result = result;
-      return await result.asFuture;
-    }());
-    return resultFuture;
+  ResultFuture(Future<T> future) : super(future) {
+    Result.capture(future).then((result) {
+      _result = result;
+    });
   }
-
-  ResultFuture._(Future<T> future) : super(future);
 }