Adding vcat and tests

[thomasgudjonwright]

Closes #348.

Not sure if we want to default to a specific type of the two inputs are different, or error as I have done at this point.

[willtebbutt]

Not sure if we want to default to a specific type of the two inputs are different, or error as I have done at this point.

I suspect that we just want two methods here -- one for each isotopic type. The reason being that vcat is defined for both of them via a fallback definition -- we just want to accelerate it in cases where it's possible to accelerate.

[thomasgudjonwright]

Not sure if we want to default to a specific type of the two inputs are different, or error as I have done at this point.

I suspect that we just want two methods here -- one for each isotopic type. The reason being that vcat is defined for both of them via a fallback definition -- we just want to accelerate it in cases where it's possible to accelerate.

Ahh okay and then just let it error by itself if someone tries to pass it one of each type as the inputs?

[willtebbutt]

Ahh okay and then just let it error by itself if someone tries to pass it one of each type as the inputs?

Not quite -- it'll hit the slow fallback method, and produce a valid result, it will just do it slowly.

[willtebbutt]

LGTM. Just needs a patch bump.