Added 'a11y' and 'source' addons to storybook as well as more stories

stories/Button.stories.js

@@ -2,13 +2,16 @@ import React from 'react';
 import Button from '../src/components/Button';
 import {action} from '@storybook/addon-actions';
 import {Wrapper} from './ui';
+import {withA11y} from '@storybook/addon-a11y';
+
 
 export default {
   title: 'Button',
   component: Button,
+  decorators: [withA11y],
 };
 
-export const Simple = () => (
+export const Basic = () => (
   <Wrapper>
     <Button onClick={action('onClick')}>
       Hello Button