Change "current.value" to use new ref syntax

Author: mattfwood

stepped-solutions/Finished App/src/components/StorePicker.js

@@ -12,7 +12,7 @@ class StorePicker extends React.Component {
     // 1. Stop the form from submitting
     event.preventDefault();
     // 2. get the text from that input
-    const storeName = this.myInput.value.value;
+    const storeName = this.myInput.current.value;
     // 3. Change the page to /store/whatever-they-entered
     this.props.history.push(`/store/${storeName}`);
   };