Paddle-ernie

update to paddle-v2.0
new features:
1. auto mixed-precision training
2. gradient accumulation

Reimplemeted ERNIE with `paddle.fluid.dygraph` (a.k.a eager execution mode), featuring:

1. Pretrain and finetune ERNIE with PaddlePaddle v1.8.
1. Eager execution with paddle.fluid.dygraph.
1. Distributed training.
1. Easy deployment.
1. Learn NLP in Aistudio tutorials.
1. Backward compatibility for old-styled checkpoint

Update some new Features:

1. ERNIE-tiny: a distilled ERNIE model for faster online inference (only chinese README provided)
2. inference demo: C++ code used for CPU/GPU online inference.

Update some new Features:
1. Distillation demo.
2. Paddle High level API: Propeller
3. python3.5 & python3.7 compatibiliy

More features comming soon:
1. ERNIE Tiny
2. ERNIE Service

1. Relative position(ERNIE-gram)
1. ERNIE-gram demo
1. multicard-download