new marshmallow2-master branch

feat(marshmallow2-master): new marshmallow2-master branch

marshmallow2-master is the master branch of the marshmallow2.x.x
version, and it will not be considered compatible with the
marshmallow3.x.x version in the future.

tags will be named in 0.2.x

v0.0.8

fix marshmallow==2.x bug and optimize code.

v0.0.7

添加tags、basePath的支持，以及对marshmallow 2 支持bug修复。

v0.0.3

add unknown support.