feat(creators): unwrap functions which return promises

often, you'll want to pass some data to your promise, and it wont be prepared with partial
application in mind.
Now, we can support that by checking the return value.

BREAKING CHANGE:
functions that return promises are now treated as async

Author: Vince Speelman

src/index.js

@@ -1,7 +1,13 @@
 import { createActions as act } from 'redux-actions';
 
 const STATES = ['REQUESTED', 'RECEIVED', 'REJECTED'];
-const isPromise = value => Promise.resolve(value) === value;
+const isPromise = value => {
+  let test = value;
+  if (typeof value === 'function') {
+    test = value();
+  }
+  return Promise.resolve(test) === test;
+};
 
 const createActions = (
   { states = STATES, prefix = '' } = {

src/index.spec.js

@@ -2,7 +2,7 @@ import ca from './';
 
 const DEFAULT_MOCK = ca()()({
   PROFILE: new Promise(res => res('profile')),
-  REGISTRATION: new Promise(res => res('registered')),
+  REGISTRATION: login => new Promise(res => res('registered', login)),
   EXPLORE_STATUS: () => 'status',
   FOO: undefined,
 });