Quickfix for nesting, serialization, and postponed annotations bugs

What's Changed

• Fix bug with new Union syntax with postponed type annotations by @lebrice in #112
• Fix typos by @kianmeng in #116
• Fix nesting defaults (based on #113) by @lebrice in #115
• Add support for python 3.10, fix tests by @lebrice in #114
• Testing out GitHub actions instead of travis by @lebrice in #121
• Update badge on README by @lebrice in #122
• Try to run actions on PRs from forks too by @lebrice in #125
• Removed unnecessary state in ConflictResolver object. by @idoby in #123
• Fix #126, deserialization with postponed type ants by @lebrice in #127

New Contributors

• @kianmeng made their first contribution in #116

Full Changelog: v0.0.19...v0.0.19.post1