[Doc] Prepare v0.5.2 release (THUDM#322)

[Dataset] Add more datasets (THUDM#313)

* Add more datasets

* Prepare for v0.5.1

[Doc] Prepare v0.5 release (THUDM#311)

[Bugfix] Fix sample adj (THUDM#301)

* Fix sample_adj & docs

[Docs] Update docs & examples (THUDM#292)

* Fix docs

* Update docs

[Doc] v0.4.1 (THUDM#270)

[Doc] v0.4 release (THUDM#236)

[Doc] v0.3.0 release (THUDM#200)

[Release] New v0.2.0 release (THUDM#163)

New 0.1.2 release (THUDM#57)