[Tracking] Updating dependencies to CategoricalArrays 1.0

[ablaom]

CategoricalArrays 1.0 breaks a few things in MLJ. See here for some details. Here's the rough sequence for rolling these out:

• Update CategoricalDistributions.jl and tag as breaking, v0.2.0
• Update ScientificTypes.jl
• Update StatisticalMeasures.jl
• Update MLJBase.jl

I will do these.

Then, in no particular order, we should review the compat requirements for the following core packages. I do not expect breakages but in a few cases we might start getting dep warnings which would be good to address these early.

• MLJEnsembles.jl
• MLJBalancing.jl
• MLJTuning.jl
• MLJIteration.jl
• MLJFeatureSelection.jl

And then, some packages providing implementations of the MLJ API may need updating.

cc @DilumAluthge @devmotion