Fix nested action objects

This version fixes a bug that caused payloads to nest inside each other. See issue #23

We consider this a breaking change because some users may have worked around the bug by digging into the incorrectly created action object to get at the correct payload key.

If your project breaks when you upgrade to this version, the fix is to find code that digs into a returned action object such that you are accessing action.payload.payload and update it so that it only tries to read from the top level action.payload.

Defaults API

Breaking changes:

• actions: { action: { create () {} }} now defaults to pass the first argument through as the payload

Enhancements:

• actions: { action: { reduce () {} }} now defaults to prop assign ({...state, ...payload}) if omitted (was: Error)
• Added id = x => x utility function
• Added assign('propName') utility function to set the provided key in the state to the payload value.
• You can now replace the actions: { action } object with a function. It will be used as the reducer, assuming the default action creator behavior
• More documentation and examples