add Bootstrap working example

• re-organize file structure with one directory per dialog
• add index.html file per dialog
• add bootstrap styling and dynamic cdn loading
• clean up react code and stylesheet

npm setup script update

adds force flag
"setup": "rm -f .clasp.json ..."

Update README.md

Move clasp to devDependencies

update dynamic cdn urls

Add repository field

src/client/dialog-demo-bootstrap/index.js

@@ -0,0 +1,7 @@
+import React from 'react';
+import ReactDOM from 'react-dom';
+import SheetEditor from './components/SheetEditor';
+
+import './styles.css';
+
+ReactDOM.render(<SheetEditor />, document.getElementById('index'));