Susi

- [ADDED] New distance metric "spectralangle".
- [ADDED] FAQs.
- [ADDED] Separate between positional and keyword parameters.
- [ADDED] Plot script for neighborhood distance weight matrix.
- [FIXED] Added inherited members to code documentation.

- [ADDED] Logo.
- [ADDED] SOMPlots documentation.
- [REMOVED] Python 3.5 support. Now, only 3.6-3.8 are supported.
- [FIXED] Scikit-learn warnings regarding validation of positional arguments.
- [FIXED] Sphinx documentation warnings.

- [ADDED] Support for Python 3.8.x.
- [ADDED] Test coverage and MultiOutput test.
- [CHANGED] Function `setPlaceholder` to `set_placeholder`.
- [FIXED] Documentation links

- [ADDED] Documentation of the hyperparameters.
- [ADDED] Plot scripts.
- [CHANGED] Structure of the module files.

- [FIXED] Replaced scikit-learn `sklearn.utils.fixes.parallel_helper`, see 12.

- [ADDED] Optional tqdm visualization of the SOM training
- [ADDED] New `init_mode_supervised` called `random_minmax`.
- [CHANGED] Official name of package changes from `SUSI` to `SuSi`.
- [CHANGED] Docstrings for functions are now according to guidelines.
- [FIXED] Semi-supervised classification handling, sample weights
- [FIXED] Supervised classification SOM initalization of `n_iter_supervised`
- [FIXED] Code refactored according to prospector
- [FIXED] Resolved bug in `get_datapoints_from_node()` for unsupervised SOM.