Beam Search

[zhang-jinyi]

Hi，

Great code！
I'm wondering which steps are necessary to move the greedy decoder from currently implemented to an actual beam search decoder.
Could you tell me which is the right point in the code where to add this functionality?

refer http://stackoverflow.com/questions/37027665/implementing-seq2seq-with-beam-search
and tensorflow/tensorflow#654

https://github.com/tensorflow/tensorflow/blob/34df7ee6f5a8f931d2433dc7e6e739bc880a35ea/tensorflow/contrib/seq2seq/python/ops/decoder.py the dynamic_decode was built to ，with beam search

Thanks a lot!