Further improve entropy.py functions

[PanPip]

According to @rspadim, functions in entropy.py could use numpy array instead of strings, as it's better to numba.

Guide on how to implement this is available in the comments in PR #311 .

[rspadim]

this could be used to others parts too, like https://github.com/hudson-and-thames/mlfinlab/blob/master/mlfinlab/microstructural_features/encoding.py#L7

[kenluck2001]

Can I use this ticket as a first-time issue to fix the issue and understand the codebase?

[Jackal08]

@kenluck2001, I think so. It's from a very long time ago but I don't think we made changes.

[kenluck2001]

Hi @Jackal08, I have started to work on it.
Is this the required file: mlfinlab/mlfinlab/microstructural_features/entropy.py ?
Looking forward to confirm the exact location of the file.

[Dhavin]

Hello @Jackal08, I would like to contribute to this project by solving this issue. Can I? If @kenluck2001 has not yet been solved already?.