allow overriding API in store/action creation
throw error on override
change to use error constructor
more informative error messages
typo fix
fix accidental if condition repetition
harmonise action and store code syntax
Merge branch 'erroronoverride' of https://github.com/krawaller/refluxjs into krawaller-erroronoverride

Conflicts:
	src/createAction.js
Merge branch 'krawaller-erroronoverride'