Bump version to 0.1.1 and enhance _AutoTikTokenizer functionality

[bhavnicksm]

This pull request includes several updates to the autotiktokenizer package, focusing on version updates, improvements to the AutoTikTokenizer class, and enhancements to the test suite.

Version Updates:

• Updated the version from 0.1.0 to 0.1.1 in pyproject.toml and __init__.py to reflect the new changes. [1] [2]

Codebase Enhancements:

• Refactored the __init__ method in src/autotiktokenizer/autotiktokenizer.py to initialize bytes_encoder and bytes_decoder and added new methods _bytes_to_unicode and _normalize_token_bytes for handling byte-to-unicode conversions.
• Modified get_mergable_ranks to accept vocab and special_tokens as parameters and updated its logic to use the new _normalize_token_bytes method.
• Updated get_tiktoken_encoding to accept vocab as a parameter and adjusted related method calls accordingly.
• Refactored from_pretrained and __call__ methods to improve their functionality and added a __repr__ method for better representation.

Testing Improvements:

• Added a new fixture sample_text in tests/test_gpt2.py to provide a comprehensive text sample for testing.
• Introduced a new test test_long_text to validate the encoding and decoding of long texts, ensuring the tokenizer's accuracy and robustness.