chore: move core modules into core directory

BREAKING CHANGE:
    This change moves the http module into angular2/, so its import
    path is now angular2/http instead of http/http.

    Many other modules have also been moved around inside of angular2,
    but the public API paths have not changed as of this commit.

modules/angular2/src/facade/async.dart

@@ -1,126 +0,0 @@
-library angular2.core.facade.async;
-
-import 'dart:async';
-export 'dart:async' show Future, Stream, StreamController, StreamSubscription;
-
-class PromiseWrapper {
-  static Future resolve(obj) => new Future.value(obj);
-
-  static Future reject(obj, stackTrace) => new Future.error(obj,
-      stackTrace != null ? stackTrace : obj is Error ? obj.stackTrace : null);
-
-  static Future<List> all(List<dynamic> promises) {
-    return Future
-        .wait(promises.map((p) => p is Future ? p : new Future.value(p)));
-  }
-
-  static Future then(Future promise, success(value), [Function onError]) {
-    if (success == null) return promise.catchError(onError);
-    return promise.then(success, onError: onError);
-  }
-
-  static Future wrap(Function fn) {
-    return new Future(fn);
-  }
-
-  // Note: We can't rename this method to `catch`, as this is not a valid
-  // method name in Dart.
-  static Future catchError(Future promise, Function onError) {
-    return promise.catchError(onError);
-  }
-
-  static PromiseCompleter<dynamic> completer() =>
-      new PromiseCompleter(new Completer());
-}
-
-class TimerWrapper {
-  static Timer setTimeout(fn(), int millis) =>
-      new Timer(new Duration(milliseconds: millis), fn);
-  static void clearTimeout(Timer timer) {
-    timer.cancel();
-  }
-
-  static Timer setInterval(fn(), int millis) {
-    var interval = new Duration(milliseconds: millis);
-    return new Timer.periodic(interval, (Timer timer) {
-      fn();
-    });
-  }
-
-  static void clearInterval(Timer timer) {
-    timer.cancel();
-  }
-}
-
-class ObservableWrapper {
-  static StreamSubscription subscribe(Stream s, Function onNext,
-      [onError, onComplete]) {
-    return s.listen(onNext,
-        onError: onError, onDone: onComplete, cancelOnError: true);
-  }
-
-  static bool isObservable(obs) {
-    return obs is Stream;
-  }
-
-  static void dispose(StreamSubscription s) {
-    s.cancel();
-  }
-
-  static void callNext(EventEmitter emitter, value) {
-    emitter.add(value);
-  }
-
-  static void callThrow(EventEmitter emitter, error) {
-    emitter.addError(error);
-  }
-
-  static void callReturn(EventEmitter emitter) {
-    emitter.close();
-  }
-}
-
-class EventEmitter extends Stream {
-  StreamController<dynamic> _controller;
-
-  EventEmitter() {
-    _controller = new StreamController.broadcast();
-  }
-
-  StreamSubscription listen(void onData(dynamic line),
-      {void onError(Error error), void onDone(), bool cancelOnError}) {
-    return _controller.stream.listen(onData,
-        onError: onError, onDone: onDone, cancelOnError: cancelOnError);
-  }
-
-  void add(value) {
-    _controller.add(value);
-  }
-
-  void addError(error) {
-    _controller.addError(error);
-  }
-
-  void close() {
-    _controller.close();
-  }
-}
-
-class PromiseCompleter<T> {
-  final Completer<T> c;
-
-  PromiseCompleter(this.c);
-
-  Future get promise => c.future;
-
-  void resolve(v) {
-    c.complete(v);
-  }
-
-  void reject(error, stack) {
-    if (stack == null && error is Error) {
-      stack = error.stackTrace;
-    }
-    c.completeError(error, stack);
-  }
-}