Update to use prop-types module in components.

src/components/layers/MaxZoomBlock.jsx

@@ -1,4 +1,5 @@
 import React from 'react'
+import PropTypes from 'prop-types'
 
 import styleSpec from '@mapbox/mapbox-gl-style-spec'
 import InputBlock from '../inputs/InputBlock'
@@ -6,8 +7,8 @@ import NumberInput from '../inputs/NumberInput'
 
 class MaxZoomBlock extends React.Component {
   static propTypes = {
-    value: React.PropTypes.number,
-    onChange: React.PropTypes.func.isRequired,
+    value: PropTypes.number,
+    onChange: PropTypes.func.isRequired,
   }
 
   render() {