code: public static RequestToken count(String collection, int flags, BaasHandler<Long> handler) {
          return doCount(collection, null, flags, handler);
      }
docs: Asynchronously retrieves the number of documents readable to the user in <code>collection</code>
  
  @param collection the collection to doCount not <code>null</code>
  @param flags {@link RequestOptions}
  @param handler    a callback to be invoked with the result of the request
  @return a {@link com.baasbox.android.RequestToken} to handle the asynchronous request