Redux-OO-Utils: @settable improvement; minor cleanup
Redux-OO-Utils: @settable improvement; minor cleanup

- `@settable` now also generates a setter method for the reducer.  (The
  action will invoke this method instead of calling `withProps`
  directly.)
- Replaced Object.defineProperty with simple assignment, which is
  sufficient.

hcschuetz/todomvc-redux-oo,hcschuetz/todomvc-redux-oo