When I try to use the Flexslider with 'built-in' jquery, the Flexslider won't work. When I use my own **myjquery** file, It works as if nothing ever.  
Do I always have to use my own jquery file even wordpress has its own?

- Wordpress' (built in) jQuery vserion: 1.11.3  
- Flexbox required jQuery version: 1.7+  
- **myjquery** = jquery version: 1.12.0

Summary: flexbox should work with jQuery of WordPress.

------------
### Briefly
Flexslider doesn't work when I use Wordpress' jQuery.
It works when I add my own **myjquery.js** which is jquery 1.12.0 and when I dequeue original jquery `wp_dequeue_script('jquery');`.  
It looks like WordPress' jQuery is not visible for my Flexslider and custom.js file.

Errors:
When I run the site with WordPress with its own jQuery there is one error:  
`$ is not a function` file: 'custom.js:2:1' what means that jquery is not found but it's included in header (I've checked).
_When I use 'myjquery' there is no errors and plugin works correctly._

The content of 'custom.js':
```
$(window).load(function() {
  $('.flexslider').flexslider({
    animation: "slide"
  });
});
```

--------
Register and include styles & scripts:

    wp_register_script( 'bootstrap-js', get_template_directory_uri() . '/bootstrap/js/bootstrap.js' );
    wp_register_script( 'myjquery', get_template_directory_uri() . '/js/jquery.js' );
    wp_register_script( 'flexslider', get_template_directory_uri() . '/js/flexslider.js', array('jquery'), false, true );
    wp_register_script( 'custom-js', get_template_directory_uri() . '/js/custom.js', array('flexslider'), false, true );
    
    // Enqueue :: styles & scripts
    function mytheme_enqueue_items() {
      wp_enqueue_style( 'my-main-css' );
      wp_enqueue_style( 'bootstrap-css' );
      wp_enqueue_style( 'bootstrap-responsive' );
      wp_enqueue_style( 'flexslider-css' );
    
      // wp_enqueue_script( '**myjquery**' ); // **flexslider works correctly when uncommented**
      wp_enqueue_script( 'bootstrap-js' );
      wp_enqueue_script( 'flexslider' );
      wp_enqueue_script( 'custom-js' );
    }
    add_action( 'wp_enqueue_scripts', 'mytheme_enqueue_items' );