title: mapStateToProps must return an object. Instead received Map {}?
body: <p>Hello i use Immuteble Map for state and when i try maspStateToProps i have this error. </p>
  
  <blockquote>
    <p>Uncaught Invariant Violation: <code>mapStateToProps</code> must return an object.
    Instead received Map {}.</p>
  </blockquote>
  
  <p>Here is my code:</p>
  
  <p>Component:</p>
  
  <pre><code>    const mapStateToProps = (state) =&gt; {
        return state
      }
  
       class LoanCalculator extends React.Component{
  
        componentWillMount(){
         this.dispatch(loadConstraints());
       }
  
        render(){
          return (
            &lt;div&gt;
              &lt;h1&gt; Loan Calculator &lt;/h1&gt;
              &lt;SlidersBox {...this.props}/&gt;
           &lt;/div&gt;
         )
       }
     }
  
      LoanCalculator = connect(
        mapStateToProps
      )(LoanCalculator)
  
     export default LoanCalculator
  </code></pre>
  
  <p>REDUCER</p>
  
  <pre><code>    import { Map } from 'immutable'
      import {LOAD_CONSTRAINTS, SET_AMOUNT_VALUE, SET_TERM_VALUE} from "../actions/actions";
  
      const initialState = new Map();
  
      export default function calculator(state = initialState, action){
        switch (action.type){
          case LOAD_CONSTRAINTS:
            return  state.set("constraints", action.constraints)
           case SET_AMOUNT_VALUE:
             return state.set("selectedAmount", action.amount)
          case SET_TERM_VALUE:
           return state.set("selectedTerm", action.term)
          default:
            return state
        }
      }
  </code></pre>