BiLSTM

参考：
https://github.com/createmomo/CRF-Layer-on-the-Top-of-BiLSTM
https://createmomo.github.io/2017/09/12/CRF_Layer_on_the_Top_of_BiLSTM_1/
https://createmomo.github.io/2017/09/23/CRF_Layer_on_the_Top_of_BiLSTM_2/
https://createmomo.github.io/2017/10/08/CRF-Layer-on-the-Top-of-BiLSTM-3/
https://createmomo.github.io/2017/10/17/CRF-Layer-on-the-Top-of-BiLSTM-4/
https://createmomo.github.io/2017/11/11/CRF-Layer-on-the-Top-of-BiLSTM-5/
https://createmomo.github.io/2017/11/24/CRF-Layer-on-the-Top-of-BiLSTM-6/
https://createmomo.github.io/2017/12/06/CRF-Layer-on-the-Top-of-BiLSTM-7/
https://createmomo.github.io/2017/12/07/CRF-Layer-on-the-Top-of-BiLSTM-8/