Release ERNIE 2.0

ERNIE 2.0 is a continual pre-training framework for language understanding in which pre-training tasks can be incrementally built and learned through multi-task learning

add utils/init.py

test=develop
fix #215

fix #212

modify_readme,test=develop

test=develop

enable gc for predict_classify

add classify inference using infer_program

fix #207

add ce  for ELMo

update

add import random

fix #200

fix a typo

add predict_classifier.py

fix #152

add ce for ERNIE

add ce for BERT

add check_cuda for ERNIE

Add cuda check for bert

[NOT MERGE]Support multi process training for BERT

modify elmo README.md

 fix pyreader return empty array as None in paddle 1.5

fix #151
paddle 1.4 does not occur this problem