Changed register_entity to create_token

[neilong31]

Fixes #113

Changes all instances of register_entity to create_token. Including the README.md

The only place I didn't touch was CHANGELOG.md

[codecov]

Codecov Report

Merging #118 into master will decrease coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #118      +/-   ##
==========================================
- Coverage   88.05%   88.01%   -0.05%     
==========================================
  Files           7        6       -1     
  Lines         268      267       -1     
  Branches       31       31              
==========================================
- Hits          236      235       -1     
  Misses         25       25              
  Partials        7        7

Impacted Files	Coverage Δ
flask_jwt_router/_jwt_routes.py	100% <ø> (ø)	⬆️
flask_jwt_router/_entity.py	76.78% <ø> (ø)	⬆️
flask_jwt_router/_authentication.py	90.9% <100%> (ø)	⬆️
flask_jwt_router/_jwt_router.py	89.47% <100%> (ø)	⬆️
flask_jwt_router/__init__.py

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[joegasewicz]

Great work @neilong31