* add all wiki embedding and part of baidu encyclopedia embedding.

* add embedding example

* add people_daily, weibo, sougou pretrained embedding

* add zhihu, finacial,literature embedding

* Add embedding model readme; add embedding train example and readme

* fix README example

* fix embedding doc

* add paddle.models api reference docs

* update docs

* update docs

* update docs

* tmp

* update docs

* update docs

* update docs

* update docs

* update docs

* update docs

* add model api

* update codes

* update codes

* update codes