bump paddlehub to v2.3.1 (#2147)

Update version

Update releaes note.

Update version

Add electra modules (#1173)

* Add electra modules

* Amend module versions of chinese-bert-wwm, chinese-bert-wwm-ext, rbt3 and rbtl3

* Updata demo README.md

Add thanks

Update installation.md

Update sentence_sim.md

 add unitest, config, fix ernie_gen bugs and add ernie_tiny_couplet (…

…#782)

Update release.md