ERNIE with paddle 2.1

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

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.
2. Eager execution with paddle.fluid.dygraph.
3. Distributed training.
4. Easy deployment.
5. Learn NLP in Aistudio tutorials.
6. 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

update some new features:

1. auto mixed precision training
2. multi-processing training
3. python3 compatibility

more features coming soon:

1. ERNIE Service
2. Distillation