rails generate component builds an unusable component

[DanielMSchmidt]

Hi there,

First of all thanks for this great lib!

The bug I encountered is neither critical, nor hard to fix:
If you type rails g react:component SubscriptionForm subscribable_type:string subscribable_id:number you get a component which looks like this:

var SubscriptionForm = React.createClass({
  propTypes: {
    subscribableType: React.PropTypes.string,
    subscribableId: React.PropTypes.number
  },

  render: function() {
    return (
      <div>
        <div>Subscribable Type: {this.props.subscribable_type}</div>
        <div>Subscribable: {this.props.subscribable_id}</div>
      </div>
    );
  }
});

So the either the propTypes or the props used in the render function are correct. If I find time later I will maybe add a PR.

Regards!