Add user dissimilarity matrix

[davins90]

Hi, first of all, thanks for your precious work. I have this suggestion: for the categorical variable is is possible to add a precomputed dissimilarity matrix (like from gower function)?

Thanks

[nicodv]

Not supported yet, and might be a pretty hefty refactor to add it. Although not too fundamentally complex.

I would honestly say this is not a priority for me, so... PRs are welcome. :)