Implement library of categorical statistics.

[fernando-aristizabal]

Generate a sub-package, module, or class of basic level categorical statistics.

This issue is related to by independent to #17.

Current behavior

• No functions to compute categorical statistics are being computed.

Expected behavior

• We need to have a sub-package, module, or class of basic level categorical statistics.
• These functions should be two or multi class agnostics only accepting TP, TN, FP, and FNs=None as input.
• Some basic examples include MCC, CSI, TPR, F1-Score, Precision, Recall, Accuracy, FAR, etc.
• How do we account for functions that are mathematically equivalent but go by differing names?
• How do we account for cases where users can pass strings to denote which statistics to compute?
• Including references for every statistics.
• Further functionality should be later generated to apply these functions to the contingency table structures proposed in Create categorical contingency table data structure #17.

[fernando-aristizabal]

Closed via #65.