title: Failed prop type: Invalid prop of type `function` supplied expected a single ReactElement
body: <p>I'm trying to make a post using react v4 and axios, I was following <a href="https://www.youtube.com/watch?v=SX5HkOP-LWs&amp;index=7&amp;list=PLuNEz8XtB51K-x3bwCC9uNM_cxXaiCcRY" rel="nofollow noreferrer">this tutorial</a> and I did exactly as he said, but I'm getting an error:
  Maybe because I'm using another version of react, how can fix it?</p>
  
  <blockquote>
    <p>Failed prop type: Invalid prop <code>userSignupRequest</code> of type <code>function</code>
    supplied to <code>SignUp</code>, expected a single ReactElement.</p>
  </blockquote>
  
  <p><strong>here is my code:</strong> </p>
  
  <pre><code>import React from 'react';
  import SignUpForm from './SignUpForm';
  import { connect } from 'react-redux';
  import { userSignupRequest } from '../../actions/signupActions';
  import PropTypes from 'prop-types';
  
  class SignUp extends React.Component{
    render(){
      const { userSignupRequest } = this.props;
      return(
          &lt;SignUpForm userSignupRequest={userSignupRequest}/&gt;
      );
    }
  }
  
  
  SignUp.propTypes = {
    userSignupRequest: PropTypes.element.isRequired
  }
  
  export default connect(null, { userSignupRequest })(SignUp);
  </code></pre>
  
  <p><strong>SignUp Actions:</strong></p>
  
  <pre><code>import axios from 'axios';
  import Constants from '../components/Constants'
  
  export function userSignupRequest(userData) {
    return dispatch =&gt; {
      return axios.post(Constants.URL_REGISTER, userData);
    }
  }
  </code></pre>