title: Schedulers.io() not returning to main thread
body: <p>I'm using RxParse to parse query's async load but when i subscribe my observable using subscribeOn(Schedulers.io()) my onCompleted method is never called on main thread. Instead of this, my onCompleted method is called inside of worker thread pool. If i use observeOn(AndroidSchedulers.mainThread) everything will work as well, but my onNextMethod will be called on main thread too and I don't want it.</p>
  
  <p>There is something wrong in my code?</p>
  
  <p>Have anything wrong in my code?</p>
  
  <pre><code>ParseObservable.find(myQuery)
      .map(myMapFunc())
      .subscribeOn(AndroidSchedulers.handlerThread(new Handler()))
      .subscribe(
          new Subscriber&lt;MyObj&gt;() {
             @Override
              public void onError(Throwable e) {
                  Log.e("error","error",e);
              }
  
              @Override
              public void onNext(T t) {
                  // ... worker thread (but here is ok)
              }
  
              public void onCompleted() {
                  // ... worker thread again instead of mainThread
              }
          }
      )
  );
  </code></pre>