code: public void deleteDocument(Task task) throws ConflictException, DocumentNotFoundException, DocumentStoreException {
          this.mDocumentStore.database().delete(task.getDocumentRevision());
      }
docs: Deletes a Task document within the DocumentStore.
  @param task task to delete
  @throws ConflictException if the task passed in has a rev which doesn't
  match the current rev in the DocumentStore.
  @throws DocumentNotFoundException if the rev for this task does not exist
  @throws DocumentStoreException if there was an error deleting the rev for this task