fix eslint issues

src/core/components/app.jsx

@@ -1,4 +1,5 @@
-import React, { PropTypes } from "react"
+import React from "react"
+import PropTypes from "prop-types"
 
 export default class App extends React.Component {
 
@@ -6,7 +7,7 @@ export default class App extends React.Component {
     let { getComponent, layoutSelectors } = this.props
     const layoutName = layoutSelectors.current()
     const Component = getComponent(layoutName, true)
-    return Component ? Component : ()=> <h1> No layout defined for "{layoutName}" </h1>
+    return Component ? Component : ()=> <h1> No layout defined for &quot;{layoutName}&quot; </h1>
   }
 
   render() {