Pyspellchecker

* Add ability to load multiple languages at once; [see discussion](https://github.com/barrust/pyspellchecker/discussions/97)
* Fix default tokenizer to not enforce lower case; [99](https://github.com/barrust/pyspellchecker/issues/99)

* Deprecated `spell.word_probability` since the name makes it seem that it is building a true probability; use `spell.word_usage_frequency` instead
* Added Russian language dictionary; [91](https://github.com/barrust/pyspellchecker/pull/91) Thanks [sviperm](https://github.com/sviperm)
* Include `__iter__` to both the `SpellChecker` and `WordFrequency` objects

* ***Remove*** *python 2.7* support
* Updated automated `scripts/build_dictionary.py` script to support adding missing words
* Updated `split_words()` to attempt to better handle punctuation; 84
* Load pre-built dictionaries from relative location for use in PyInstaller and other executable tools; 64

* ***NOTE:*** Last planned support for **Python 2.7**
* All dictionaries updated using the `scripts/build_dictionary.py` script

* Remove `encode` from the call to `json.loads()`

* Reduce words in __edit_distance_alt to improve memory performance; thanks [blayzen-w](https://github.com/blayzen-w)