Performance Improvement by caching values

[bubuntux]

when faker is used to return consistent values based on a seed values there is a big performance issue since the yml files are re-read every time, caching the values per local prevent this issue.

after this fix the tests run significantly faster for comparative the tests in this project take ~50seconds, after this fix, tests went down to ~13seconds the gain are significantly better in bigger projects when this library is being used

[bubuntux]

@codingricky @LC24 hey there, can you guys can take a look at these changes?

[bodiam]

@bubuntux this project is dead, but these changes have already been incorporated in datafaker version 1.2.0, which is currently on maven central

[bubuntux]

@bodiam thanks for the heads up i'll take a look