* 0.29.3

* modify: label relate methods

* modify: label method

* modify: make tag class be better.

* modify: change return type of method tags() from string[] to Tag[], and implemented all methods relates to Label.

* modify: bump version

* modify: change createTag() to getOrCreateTag()

* Refactor Tag Design

* Refine Tag design

* 0.29.41

* remove findAll for Tag class

* add todo for check tag before delete
Co-authored-by: Huan (李卓桓) <zixia@zixia.net>