As a heads up for everybody, most of the current ng-bootstrap package is incompatible with the newest release of bootstrap (Alpha 6), including all collapsing media (collapses, dropdowns, navs, etc.).
I haven't yet found out how to make the package working, I assume that the package is using tags that bootstrap stopped supporting. I suppose we will have to simply wait until the dev changes all the tags, which could take a very long time (bootstrap alpha 6 is basically a re-write...).
If anybody has got a hack to get ng-bootstrap and bootstrap alpha 6 to play nice, let us know!
The ng-bootstrap project just released version 1.0.0-alpha.18 with full support for Bootstrap 4.0.0-alpha.6. All the directives are now working with Bootstrap's 4.0.0-alpha.6 CSS.