consider refined similarity metric based on Categorical versus Continuous features

[mlopatka]

https://github.com/mozilla/python_mozetl/blob/491fbda515f985f3156ff0c70859624fd4961ea8/mozetl/taar/taar_similarity.py#L248

Consider emphasizing the categorical features more by adding a 1-h(x,y) when using hamming distance.