Replace var with const (#743)

Author: pocketcolin

README.md

@@ -25,23 +25,23 @@ The JavaScript ecosystem is wide and incorporates a large number of platforms an
 To use the npm modules for a browser based application, include it as you normally would:
 
 ```js
-var Parse = require('parse');
+const Parse = require('parse');
 ```
 
 For server-side applications or Node.js command line tools, include `'parse/node'`:
 
 ```js
 // In a node.js environment
-var Parse = require('parse/node');
+const Parse = require('parse/node');
 ```
 
 For React Native applications, include `'parse/react-native'`:
 ```js
 // In a React Native application
-var Parse = require('parse/react-native');
+const Parse = require('parse/react-native');
 
 // On React Native >= 0.50 and Parse >= 1.11.0, set the Async
-var AsyncStorage = require('react-native').AsyncStorage;
+const AsyncStorage = require('react-native').AsyncStorage;
 Parse.setAsyncStorage(AsyncStorage);
 ```