Update assets/js/admin-scripts.js

Update admin-scripts.js to allow for new Media Uploader.
Update includes/admin/downloads/metabox.php

Added blank data attributes, can be modified to control the title and button text of the media uploader: 
data-uploader_title 
data-uploader_button_text
Update includes/admin/downloads/metabox.php

The difference between data-uploader_button_text="Insert" and data-uploader_button_text="" is small but important!
Update includes/admin/downloads/metabox.php

Pippin: Can you go ahead and localize it?
<?php _e( 'Insert', 'edd' ); ?>
me: Stoopid me! yes, think before commit Mike!
Merge pull request #822 from MadeByMike/patch-8

New Media Uploader