Cannot apply any Bootstrap style in using React-bootstrap library
<p>I want to use default Bootstrap components in my React application, so I'm using React-bootstrap NPM-package. But I stuck at the very beginning: I cannot use any <a href="https://react-bootstrap.github.io/components.html" rel="nofollow noreferrer">default component</a> although I'm just copying very simple exmaples from official docs. Every time I use Bootstrap-styled component, I get basic component withouts styles. For example the code below renders a <code>&lt;button&gt;</code> without styles, not <code>&lt;Button bsStyle="danger"&gt;</code> from Bootstrap.</p>

<pre><code>import React from "react";
import ReactDOM from "react-dom";
import {Provider} from 'react-redux';
import store from "./store";
import {Button} from 'react-bootstrap';

class App extends React.Component {
    render() {
        return (
            &lt;Provider store={store}&gt;
                &lt;Button bsStyle="danger"&gt;Danger&lt;/Button&gt;
            &lt;/Provider&gt;
        );
    }
}

ReactDOM.render(&lt;App/&gt;, document.getElementById('app-container'));
</code></pre>

<p>Why do I have such a problem? Maybe it's about Babel or Webpack: some styles are being ignored during the packaging?</p>