Add comprehensive test suites for Vicinity and utility functions

- Implemented `test_utils.py` with tests for vector normalization functions
- Created `test_vicinity.py` with extensive test cases covering Vicinity class methods
- Added `test_huggingface.py` to test Hugging Face integration functionality
- Included tests for various scenarios such as:
  * Initialization and vector handling
  * Querying and thresholding
  * Insertion and deletion of vectors
  * Saving and loading vector stores
  * Handling non-serializable items
  * Hugging Face Hub integration

Author: davidberenstein1957