feat(index.js): export components

BREAKING CHANGE: named exports changes for ToastMessage

Before:

```js
import { ToastContainer, ToastMessage } from "react-toastr"

const ToastMessageFactory = React.createFactory(ToastMessage.animation);
const jQueryFactory = React.createFactory(ToastMessage.jQuery);

<ToastContainer toastMessageFactory={ToastMessageFactory} />
<ToastContainer toastMessageFactory={jQueryFactory} />
```

After:

```js
import { ToastContainer, ToastMessageAnimated } from "react-toastr"
import ToastMessagejQuery from "react-toastr/lib/components/ToastMessage/ToastMessagejQuery";

const ToastMessageFactory = React.createFactory(ToastMessageAnimated);
const jQueryFactory = React.createFactory(ToastMessagejQuery);

<ToastContainer toastMessageFactory={ToastMessageFactory} />
<ToastContainer toastMessageFactory={jQueryFactory} />
```

src/__tests__/index.test.js

@@ -0,0 +1,9 @@
+import { ToastContainer, ToastMessage, ToastMessageAnimated } from "../index"
+
+describe(`index module`, () => {
+  it(`should be exported as ES2015 module`, () => {
+    expect(ToastContainer).toBeDefined()
+    expect(ToastMessage).toBeDefined()
+    expect(ToastMessageAnimated).toBeDefined()
+  })
+})

src/index.js

@@ -1,9 +1,7 @@
-import React from 'react';
-import ReactDOM from 'react-dom';
-import App from './app/App';
-import './index.css';
+export { ToastContainer } from "./components/ToastContainer"
 
-ReactDOM.render(
-  <App />,
-  document.getElementById(`root`)
-);
+export { ToastMessage } from "./components/ToastMessage/ToastMessage"
+
+export {
+  ToastMessageAnimated,
+} from "./components/ToastMessage/ToastMessageAnimated"