Proto-plus-stubs

What's Changed
* Improve message base class by henribru in https://github.com/henribru/proto-plus-stubs/pull/2


**Full Changelog**: https://github.com/henribru/proto-plus-stubs/compare/v0.2.0...v0.3.0

What's Changed
* Add generic overloads by henribru in https://github.com/henribru/proto-plus-stubs/pull/1
* [Loosen version requirements](https://github.com/henribru/proto-plus-stubs/commit/494904342d6c552019ff41198098513b9e927519)

**Full Changelog**: https://github.com/henribru/proto-plus-stubs/compare/v0.1.0...v0.2.0

**Full Changelog**: https://github.com/henribru/proto-plus-stubs/commits/v0.1.0