* add some document for pretraining.

* refine ernie-1.0 document.

* refine ernie-1.0 document.

* remove pre-train document.

* Update README.md

* add infer script.

* refine

* remove h5py requirement

* move export to paddlenlp.transformers.export_model

* move export to paddlenlp.transformers.export_model

* fix docs.

* fix as reviews.