Added drawing endpoint tests

Also refactored ImageTests away from BrowserKit
Also added image upload type validation.

tests/BrowserKitTest.php

@@ -13,13 +13,6 @@ abstract class BrowserKitTest extends TestCase
 
     use DatabaseTransactions;
 
-    /**
-     * The base URL to use while testing the application.
-     *
-     * @var string
-     */
-    protected $baseUrl = 'http://localhost';
-
     // Local user instances
     private $admin;
     private $editor;