Add tag with name of console command

Listen for the `CommandStarting` event and add a tag with the name of the console command. This makes it easy to know which console command has the error.

Note: I did not typehint `ComandStarting` in `commandStartingHandler` because then I think it would only work on Laravel >=5.5 and based on the documentation this package supports Laravel 5.*. I'm surprised that the typehint of `MessageLogged` on  `messageLoggedHandler` does not cause issues for people trying to use older versions of Laravel since `MessageLogged` was not added until Laravel 5.4.

Author: ejunker

src/Sentry/SentryLaravel/SentryLaravelEventHandler.php

@@ -27,6 +27,8 @@ class SentryLaravelEventHandler
 
         'illuminate.log' => 'log',           // Until Laravel 5.3
         'Illuminate\Log\Events\MessageLogged' => 'messageLogged', // Since Laravel 5.4
+        
+        'Illuminate\Console\Events\CommandStarting' => 'commandStarting', // Since Laravel 5.5
     );
 
     /**
@@ -223,6 +225,18 @@ protected function messageLoggedHandler(MessageLogged $logEntry)
         ));
     }
 
+    /**
+     * Since Laravel 5.5
+     *
+     * @param Illuminate\Console\Events\CommandStarting $event
+     */
+    protected function commandStartingHandler($event)
+    {
+        $this->client->tags_context(array(
+            'command' => $event->command,
+        ));
+    }
+    
     /**
      * Since Laravel 5.3
      *