Lipschitz and Hurwitz quaternions

[chrisvwx]

My understanding is that the current implementation of Quaternions with Int inputs is aligned with the idea of a Lipschitz quaternion.

julia> Quaternion(1,2,3,4)
Quaternion{Int64}(1, 2, 3, 4, false)

On the other hand, in many cases one wants a Hurwitz quaternion. Even though I don't have a clear idea how a Hurwitz quaternion would be integrated with this package, I thought perhaps an issue about it would at least provide a place to discuss the topic.

[hyrodium]

I think this issue is solved with HalfIntegers.jl. It would be nice to have more documentation for Hurwitz quaternions.