title: Importing Editor from draft-js-plugins-editor causes TypeErrors on empty project
body: <p>I've created a new React project in Webstorm. I've installed <code>draft-js</code> and <code>draft-js-plugins-editor</code>, along with the plugins <code>draft-js-hashtag-plugin</code> and <code>draft-js-mathjax-plugin</code> (Using node).</p>
  
  <p>I've following their 'getting started' <a href="https://github.com/draft-js-plugins/draft-js-plugins" rel="nofollow noreferrer">on their Github</a>, however the example doesn't work for me. As soon as I write</p>
  
  <p><code>import Editor from 'draft-js-plugins-editor';</code></p>
  
  <p>I get an <code>TypeError: Cannot read property 'object' of undefined</code> error.</p>
  
  <pre><code>./node_modules/draft-js-plugins-editor/lib/Editor/index.js
  node_modules/draft-js-plugins-editor/lib/Editor/index.js:177
  174 | }(_react.Component);
  175 |
  176 | PluginEditor.propTypes = {
      &gt; 177 |   editorState: _react2.default.PropTypes.object.isRequired,
  178 |   onChange: _react2.default.PropTypes.func.isRequired,
  179 |   plugins: _react2.default.PropTypes.array,
  180 |   defaultKeyBindings: _react2.default.PropTypes.bool,
  </code></pre>
  
  <p>My minimal example code:</p>
  
  <pre><code>import React, { Component } from 'react';
  import Editor from 'draft-js-plugins-editor'; // Error upon doing this
  import createHashtagPlugin from 'draft-js-hashtag-plugin';
  import { EditorState } from 'draft-js';
  
  const hashtagPlugin = createHashtagPlugin();
  
  const plugins = [
      hashtagPlugin,
  ];
  
  export default class MyEditor extends Component {
  
      state = {
          editorState: EditorState.createEmpty(),
      };
  
      onChange = (editorState) =&gt; {
          this.setState({
              editorState,
          });
      };
  
      render() {
          return (
              &lt;Editor
                  editorState={this.state.editorState}
                  onChange={this.onChange}
                  plugins={plugins}
              /&gt;
          );
      }
  }
  </code></pre>