fix(subscriptions): fixes bug that tracked subscriber subscriptions twice.

Author: trxcllnt

src/Observable.ts

@@ -91,7 +91,11 @@ export class Observable<T> implements Subscribable<T> {
     const { operator } = this;
     const sink = toSubscriber(observerOrNext, error, complete);
 
-    sink.add(operator ? operator.call(sink, this) : this._subscribe(sink));
+    if (operator) {
+      operator.call(sink, this);
+    } else {
+      sink.add(this._subscribe(sink));
+    }
 
     if (sink.syncErrorThrowable) {
       sink.syncErrorThrowable = false;

src/operator/groupBy.ts

@@ -76,9 +76,7 @@ class GroupBySubscriber<T, K, R> extends Subscriber<T> implements RefCountSubscr
               private keySelector: (value: T) => K,
               private elementSelector?: (value: T) => R,
               private durationSelector?: (grouped: GroupedObservable<K, R>) => Observable<any>) {
-    super();
-    this.destination = destination;
-    this.add(destination);
+    super(destination);
   }
 
   protected _next(value: T): void {