v1.9.0

Enhancements

• Add Decimal.negate/1
• Add Decimal.apply_context/1
• Add Decimal.normalize/1
• Add Decimal.Context.with/2, Decimal.Context.get/1, Decimal.Context.set/2,
  and Decimal.Context.update/1
• Add Decimal.is_decimal/1

Deprecations

• Deprecate Decimal.minus/1 in favour of the new Decimal.negate/1
• Deprecate Decimal.plus/1 in favour of the new Decimal.apply_context/1
• Deprecate Decimal.reduce/1 in favour of the new Decimal.normalize/1
• Deprecate Decimal.with_context/2, Decimal.get_context/1, Decimal.set_context/2,
  and Decimal.update_context/1 in favour of new functions on the Decimal.Context module
• Deprecate Decimal.decimal?/1 in favour of the new Decimal.is_decimal/1