title: update RecyclerView with Android LiveData
body: <p>There are many examples how to push new list to adapter on LiveData change.</p>
  
  <p>I'm trying to update one row (e.g number of comments for post) in the huge list. It would be stupid to reset whole list to change only one field.</p>
  
  <p>I am able to add observer onBindViewHolder, but I can't understand when should I remove observer</p>
  
  <pre><code>@Override
  public void onBindViewHolder(ViewHolder vh, int position) {
      Post post = getPost(position);
      vh.itemView.setTag(post);
      post.getLiveName().observeForever(vh.nameObserver);
      ... 
  }
  </code></pre>