Webpack hmr support WIP

[c-jacquin]

no docs, no tests, not really sure ... but it works just fine.

if (module.hot) {
  module.hot.accept('./actions', () => {
    store.hmrUpdate({
      handlers: require('./actions').default,
    });
  });

  module.hot.accept('./epics', () => {
    store.hmrUpdate({
      epics: require('./epics').default,
    });
  });

  module.hot.accept('./effects', () => {
    store.hmrUpdate({
      effects: require('./effects').default,
    });
  });
}