kmeans weights variance parallelization

See merge request !54

[gmm] Simply calls to functions by passing GMM machine around

Closes #38

See merge request !52

[gmm] deduplicate EM training code

Closes #39

See merge request !51

improve variance estimation speed in kmeans, convert data to proper arrays

See merge request !50

Fix np memory issues and rename k_means to kmeans

Closes #42, #40, and #37

See merge request !49