As we have established already, jQuery 1.x does not correctly handle
`data-*` attributes where there are multiple dashes. This makes it
so we can still handle nested options when working with jQuery 1.x
by using the `.dataset` option that is supported by all major
browsers as well as IE 11+.
Browser support tables for the `.dataset` attributes can be found at
http://caniuse.com/dataset
A notice was already added to the documentation about this in
caeb0ec9b7.
The related ticket in the jQuery repository about this issue is
https://github.com/jquery/jquery/issues/2070.
This closes https://github.com/select2/select2/issues/2969.
