* add new seq2seq example: rnn_search (#3574)

* re-commit seq2eq example: rnn search

* add new_seq2seq examples: rnn_search and vae_text

* modify dataset description in vae_text/README.md

* modify vae_text/README.md and vae_text/download.py

* update vae_text/infer.sh and vae_text/README.md

* add multi-gpu support for rnn_search; fix windows support for rnn_search and vae_text

* remove parallel argument in args.py

* remove hard codes

* remove hard codes

* update download.py for windows download

* fix model path for windows in vae_text/infer.py

* fix python2 utf-encoding

* fix utf-8 error in python2 when predict (#3721)

* change rnn_search to seq2seq; change vae_text to variational seq2seq (#3734)

* re-commit seq2eq example: rnn search

* add new_seq2seq examples: rnn_search and vae_text

* modify dataset description in vae_text/README.md

* modify vae_text/README.md and vae_text/download.py

* update vae_text/infer.sh and vae_text/README.md

* add multi-gpu support for rnn_search; fix windows support for rnn_search and vae_text

* remove parallel argument in args.py

* remove hard codes

* remove hard codes

* update download.py for windows download

* fix model path for windows in vae_text/infer.py

* fix python2 utf-encoding

* change rnn_search to seq2seq; change vae_text to variational seq2seq

* change rnn_search to seq2seq; change vae_text to variational seq2seq

* mv variational seq2seq to variational_seq2seq

* remove old projects (#3736)

* fix use_gpu=False error (#3775)

* update_seq2seq_readme (#3783)