Hi!
Since Ionic and Bootstrap css can have conflicts between them we cannot fully support bootstrap classes on Ionic. However we're going to be adding more and more support to specific classes in a near future.
Please follow the following issues to keep up with this topic:
https://tracker.moodle.org/browse/MOBILE-2395
https://tracker.moodle.org/browse/MOBILE-2091
Cheers,
Pau