Improve DX for store creation

[gaguirre]

Ideally we should have a method createStore so we can do something like

class App extends Reduxable { ... }

const myApp = new App()
const store = myApp.createStore()

The idea would be call Redux's createStore(reducer, initialState, enhancers) with the reducer and initialState we already have from the Reduxable instance and give the user the option to pass enhancers.