Features

• Drops.Type module that allows you to define custom types (via #36)
• Drops.Type.Validator protocol that allows you to define custom validators for your types
• Added built-in Drops.Types.Number type (issue #33)
• Added union to type definition DSL (issue #37)

Fixes

• Warning about conform callback is gone (issue #34)

Changes

• All built-in types have been refactored to use the validator protocol
• Drops.Types.Sum was renamed to Drops.Types.Union