If you find the 1px jump before expanding and after collapsing when using the CSS solution a bit annoying, here's a simple JavaScript solution for Bootstrap 3...
Just add this somewhere in your code:
$(document).ready(
$('.collapse').on('show.bs.collapse hide.bs.collapse', function(e) {
e.preventDefault();
}),
$('[data-toggle="collapse"]').on('click', function(e) {
e.preventDefault();
$($(this).data('target')).toggleClass('in');
})
);