Add Poly15 support

Add Poly15 type.

Add Poly14 support

Add support for the Poly14 type.

Add Poly12 and Poly13 Types

Merge pull request #13 from mattpolzin/poly12-poly13

add Poly12 and Poly13 types.

Platformed

Introduce explicit iOS and MacOS platform minimums to the Swift package manifest.

(and again) error printout refinement

Merge pull request #10 from mattpolzin/poly-decoding-errors2

make dictionary with string keys a bit more generally recognizable as…

Another refinement to error printing

Merge pull request #9 from mattpolzin/poly-decoding-errors

try to make decoding errors easier to read.

Add Hashable conformances

All Poly types gain Hashable conformance when all generic types upon which the Poly is specialized are also Hashable.

Add the `allTypes` accessor

This accessor can be useful for generating logging based on the types a particular Poly allows.

let typeNames = Poly2<Int, Double, String>.allTypes
  .map { String(describing: $0) }
  .joined(separator: ", ")

Expose two previously internal properties on an error type.

Merge pull request #5 from mattpolzin/expose-more-error-info

Expose more error info

Add `Poly.value` accessor

Add accessor on Poly that retrieves a type-erased value.

let either = Either<Int, String>(10)
let value = either.value // type is `Any`