Tryangle

This release moves the package metadata to the pyproject.toml format and preps tryangle for the fixes to breaking changes in the new pandas, as well as prepping for the upcoming 1.0.0 release.

This release addresses dependency breaks introduced by newer versions of chainladder. From 0.2.1 onwards, Tryangle supports chainladder>=0.8.12. See 5

**Full Changelog**: https://github.com/casact/tryangle/compare/0.2.0...v0.2.1

Enhancements to the AutoEnsemble method:

- Ability to specify loss functions
- Allow non-constrained, linear, or parabolic weight functions