About RNN

----------------------reference--------------------------

1. http://www.wildml.com/2015/10/recurrent-neural-networks-tutorial-part-3-backpropagation-through-time-and-vanishing-gradients/

2. http://colah.github.io/posts/2015-08-Understanding-LSTMs/

3. https://github.com/dennybritz/rnn-tutorial-rnnlm