Correlation-toolbox package missing

Created by: didi-hou

The external package correlation-toolbox used in computing correlation coefficient and other modules are missing in the repo. It seems the toolbox is from correlation-toolbox. However, this toolbox is not released as a package on PyPI.

Not sure if the functions in the correlation-toolbox have been incorporated into scientific packages like Scipy or Elephant already since it has actually been very commonly used in many other models.