This is a known issue which many people (also Ionic users) have come across, if you search for “libsass bindings not found” then you will see many discussion threads about it.
The best solution seems to be this answer:
As you can see, the solution is that it works only with certain versions of nodejs. The problem is especially with “new” nodejs versions, e.g. nodejs v.4. I am using nodejs v.0.12 and I don’t have the problem.
Another discussion and possible solution is this post:
So that is the issue. I’ve added a warning and some info to my README because I’ve seen many people struggling with this issue.