Compatiblity with bootstrap 4

[mgvd]

Hi, in Bootstrap 4 (alpha) the class 'open' is replaced by 'show'. To make it work in version 4, I replaced it in your code,and it works fine.

Thanks for the great component.

[warmwhisky]

Hey, I changed all 'open' to 'show' in Bootstrap 4 beta 2 and didn't get the hover animation.
I changed bootstrap-dropdownhover.min.js and bootstrap-dropdownhover.min.css

[hassanbinsafdar]

Hello i changed it and make a repository use this but do not use .min.js just use js file with css and it will work in bootstrap 4 .
https://github.com/hassanbinsafdar/bootstrap-4.0-multilevel-dropdown-hover