make the usage of rnn cells compatible with TF1.1

[taochenshh]

No description provided.

[zsdonghao]

@CTTC , Many thanks for your quick PR.

After a quick check, I find you delete all blank lines between Parameters, Examples, Variables etc, it will cause readthedocs fail to build the document~ Could you keep the original document format (keep the blank lines)?

For the cell_creator can it also well work under TF1.0?

Many thanks

[taochenshh]

@zsdonghao Sorry for the deletion of the blank lines. I did not do it intentionally. I guess it's somehow done by the IDE (Pycharm) I used. I have fixed it now. And I have run it on TensorFlow 1.0. It went well. Thanks.