Accessing PropTypes via the main React package is deprecated

[rafa-3l]

Accessing PropTypes via the main React package throws a deprecation warning.
We should use the prop-types package from npm instead.

Instead of this:

User.propTypes = {
  index: React.PropTypes.number.isRequired
}

We should use this:

import PropTypes from 'prop-types';
User.propTypes = {
  index: PropTypes.number.isRequired
}