Refactored internet time option to sync server time as per review com…

…ment

README.md

@@ -152,16 +152,16 @@ npm run dev
 **4. Use internet time for issued token expiry. Default: false**
 - If this option is enabled, internet time in UTC format is fetched from the Ably service and cached every 6 hrs. 
 - This option is useful when using laravel-broadcaster on a server where, for some reason, the server clock cannot be kept synchronized through normal means.
-- Set `ABLY_USE_INTERNET_TIME` as **true** in **.env** file.
+- Set `ABLY_SYNC_SERVER_TIME` as **true** in **.env** file.
 ```dotenv
-    ABLY_USE_INTERNET_TIME=true
+    ABLY_SYNC_SERVER_TIME=true
 ```
 - Update ably section under `config/broadcasting.php` with
 ```php
         'ably' => [
             'driver' => 'ably',
             'key' => env('ABLY_KEY'),
-            'use_internet_time' => env('ABLY_USE_INTERNET_TIME', false)
+            'sync_server_time' => env('ABLY_SYNC_SERVER_TIME', false)
         ],
 ```
 

src/AblyBroadcaster.php

@@ -59,7 +59,7 @@ public function __construct(AblyRest $ably, $config)
     {
         $this->ably = $ably;
 
-        if (array_key_exists('use_internet_time', $config) && $config['use_internet_time']) {
+        if (array_key_exists('sync_server_time', $config) && $config['sync_server_time']) {
             // Local file cache is preferred to avoid sharing serverTimeDiff across different servers
             $this->serverTimeDiff = Cache::store('file')->remember('ably_server_time_diff', 6 * 3600, function() {
                 return time() - round($this->ably->time() / 1000);