add method getJobId & update doc

Author: freyo

README.md

@@ -18,7 +18,7 @@ Tencent Cloud Message Queue driver for Laravel Queue
 
 ## Configure
 
-**Laravel 5.5 uses Package Auto-Discovery, so doesn't require you to manually add the ServiceProvider.**
+**Laravel 5.5+ uses Package Auto-Discovery, so doesn't require you to manually add the ServiceProvider.**
 
 1. `config/app.php`:
 
@@ -63,13 +63,13 @@ Once you completed the configuration you can use Laravel Queue API. If you used
 
   ```php
   //use queue only
-  dispatch((new Job)->onQueue('queue-name'));
+  Job::dispatch()->onQueue('queue-name');
 
   //use topic and tag filter
-  dispatch((new Job)->onQueue('tag1,tag2,tag3'));
+  Job::dispatch()->onQueue('tag1,tag2,tag3');
 
   //use topic and routing filter
-  dispatch((new Job)->onQueue('routing-key'));
+  Job::dispatch()->onQueue('routing-key');
   ```
 
 ## Document

src/Queue/Jobs/CMQJob.php

@@ -25,6 +25,16 @@ public function __construct(Container $container, CMQQueue $connection, Message
         $this->queue      = $queue->getQueueName();
     }
 
+    /**
+     * Get the job identifier.
+     *
+     * @return string
+     */
+    public function getJobId()
+    {
+        return $this->message->msgId;
+    }
+
     /**
      * Get the raw body of the job.
      *