code: public static RequestToken count(String collection, BaasQuery.Criteria filter, BaasHandler<Long> handler) {
          return doCount(collection, filter, RequestOptions.DEFAULT, handler);
      }
docs: Asynchronously retrieves the number of documents readable to the user that match the <code>filter</code>
  in <code>collection</code>.
  
  @param collection the collection to doCount not <code>null</code>
  @param filter     a {@link BaasQuery.Criteria} to apply to the request. May be <code>null</code>
  @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