replacing outdated minified copy with up to date unminified copy

I made a recent PR to Colorbox's source, helping it to work with libraries like pjax / turbolinks where the contents of the `<body>` are emptied. This ensures that colorbox's markup exists even if one of those libraries nixed it.

Also, no need to reference the minified source, rails handles minification by default, and it's easier to view the source for debugging if the file is unminified in development environments.