Cythonize MultivariateFeatureSelector / Use Case Analysis

[srecupe2]

Multi Step: Step 1: Cythonize parallelized calculation of test statistics for each iteration Step 2: Now that Use Case potential is dramatically expanded, perform use case analysis to find the best use cases for MultivariateFeatureSelector as a transformer in classification pipeline. (highlight its most applicable situations with the best classifiers to use adjacently)

[sampan501]

@srecupe2 can you edit the description and describe each part