Since this library is for Redux users compliant to [FSA](https://github.com/acdlite/flux-standard-action/), we should fail explicitly when `handleAction` is called with a non-FSA. See #141, https://github.com/acdlite/redux-actions/pull/139#issuecomment-250376196, and https://github.com/acdlite/redux-actions/issues/140.
Since this library is for Redux users compliant to FSA, we should fail explicitly when
handleActionis called with a non-FSA.See #141, #139 (comment), and #140.