title: How to add a key to the table
body: <p>Getting this error:-
  Playing with react and react-table for the first time. Using this code:-</p>
  
  <pre><code>render() {
          const itemData = this.state.itemData;
  
          const columns = [{
              Header: 'ID',
              Cell: props =&gt; &lt;span key={props.value}&gt;{props.value}&lt;/span&gt;,
              accessor: 'ID',
  
          }, {
              Header: 'Name',
              accessor: 'name'
  
          },{
              Header: 'Description',
              accessor: 'description'
  
          }, {
              id: 'price', // Required because our accessor is not a string
              Header: 'Price',
              accessor: d =&gt; d.price // Custom value accessors!
          }]
  
  
          console.log(itemData)
          console.log(columns)
          return (
              &lt;div&gt;
                  &lt;CreateItemModal getItems={this.getItems}/&gt;
                  {_.map(itemData, () =&gt; (
                  &lt;ReactTable key={itemData.ID}
                      data={itemData}
                      resolveData={data =&gt; data.map(row =&gt; row)}
                      columns={columns}
                  /&gt;
                  ))}
              &lt;/div&gt;
          );
      }
  </code></pre>
  
  <p>Getting this error:-</p>
  
  <pre><code>index.js:2178 Warning: Each child in an array or iterator should have a unique "key" prop.
  
  Check the render method of `ItemDashboard`. 
      in ReactTable (at itemDashboard.js:77)
      in ItemDashboard (at App.js:28)
      in div (created by Segment)
      in Segment (at App.js:22)
      in App (at index.js:9)
  </code></pre>
  
  <p>ItemData is an array of this:-</p>
  
  <pre><code>ID:"78edeef0-6105-11e8-a64e-25cbecc86b8a"
  description:"hdhdhdhdhd"
  name:"this"
  price:"88888"
  </code></pre>
  
  <p>I cant seem to find the right doc to tell me how to add a key to each table row. Can you point me in the right direction?</p>
  
  <p>INITIALIZATION CODE:-</p>
  
  <pre><code>class ItemDashboard extends Component {
  
      constructor(props){
          super(props)
          this.state = {itemData: {}, item: {}, modalOpen: false}
          this.getItems = this.getItems.bind(this);
  
      }
  
      getItems(){
          API.get(apiName, path).then(response =&gt; {
              console.log(response)
              this.setState({
                  itemData: response.data
              });
          });
      }
  </code></pre>