general updates

* added exception type for empty string
* updated checks in algorithms
* updated tests
* moved to new flit publishing method using pyproject.toml

Added Levenshtein, Hamming distance, removed half-done algorithms.

Algorithm implementation:
* Added Soundex, Fuzzy Soundex, Metaphone, Lein, MRA.
* Added tests for every algorithm.
* Updated Licence.
* Added and tested some utils.