Update colorbox to work with beta 1

Working on this to make colorbox work with drupal 8 beta 1.
Some questions:
Can i require the colorbox 1.5.14 as minimun for drupal 8? I do not see a reason to use one older.
I will move the code from ColorboxSubriscriber to hook_page_build, it is the correct place for code that needs to add javascript, ok ?

I plan to make a minimum working patch, just to it work on beta 1, after this work on other parts, like fields, views and drush.