Symspellpy

- Added `separator` argument to allow user to choose custom separator for `load_dictionary`

- Added `load_bigram_dictionary` and bigram dictionary `frequency_bigramdictionary_en_243_342.txt`
- Updated `lookup_compound` algorithm
- Added `Levenshtein` to compute edit distance
- Added `save_pickle_stream` and `load_pickle_stream` to save/load SymSpell data alongside other structure (contribution by [marcoffee](https://github.com/marcoffee))

- Added `transfer_casing` to `lookup` and `lookup_compound`
- Fixed prefix length check in `_edits_prefix`

- Implemented `delete_dictionary_entry`
- Improved performance by using python builtin hashing
- Added versioning of the pickle

- Fixed `include_unknown` in `lookup`
- Removed unused `initial_capacity` argument
- Improved `_get_str_hash` performance
- Implemented `save_pickle` and `load_pickle` to avoid having to create the
dictionary every time

- Added `create_dictionary()` feature