install and use prop-types over React.PropTypes

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

package.json

@@ -70,6 +70,7 @@
     "matrix-react-sdk": "0.10.2",
     "modernizr": "^3.1.0",
     "pako": "^1.0.5",
+    "prop-types": "^15.5.10",
     "react": "^15.6.0",
     "react-dnd": "^2.1.4",
     "react-dnd-html5-backend": "^2.1.2",

src/components/views/context_menus/GenericTextContextMenu.js

@@ -16,7 +16,8 @@ limitations under the License.
 
 'use strict';
 
-import React, {PropTypes} from 'react';
+import React from 'react';
+import PropTypes from 'prop-types';
 
 export default class GenericTextContextMenu extends React.Component {
     static PropTypes = {