Add withInitializers API.

index.js

@@ -5,7 +5,7 @@ import {composeReducers} from 'redux-sac';
 import {effectsMiddleware} from 'redux-effex';
 
 export default () => {
-    let reducers = [], effects = [], middlewares = [];
+    let reducers = [], effects = [], middlewares = [], initialState;
 
     function withReducers (..._reducers) {
         reducers.push(..._reducers);
@@ -22,12 +22,18 @@ export default () => {
         return this;
     }
 
+    function withInitializers (...initializers) {
+        initialState = initializers.reduce((soFar, each) => each(soFar), initialState);
+        return this;
+    }
+
     function create () {
         return createStore(
             composeReducers(...reducers),
+            initialState,
             applyMiddleware(...middlewares, effectsMiddleware(effects))
         );
     }
 
-    return {withReducers, withMiddlewares, withEffects, create};
+    return {withReducers, withMiddlewares, withEffects, withInitializers, create};
 }