Add Python 3.13 support by updating NumPy and pandas constraints

[jbf302]

Summary

Fixes #122 by adding Python 3.13 support through conservative dependency constraint updates.

Problem

The current package constrains Python to <3.13 and requires numpy==1.*, which prevents installation on Python 3.13 since NumPy v1 doesn't support Python 3.13.

Solution

• Update requires-python constraint: >=3.6.1,<3.13 → >=3.6.1,<3.14
• Update numpy constraint: ==1.* → >=1.20,<3.0 (enables NumPy v2 support)
• Update pandas constraint: ==1.* → >=1.3,<3.0 (compatible with NumPy v2)
• Add Python 3.13 classifier

Testing Results ✅

Environment: Python 3.13.4, NumPy 2.3.2, pandas 2.3.1

• ✅ Package installs successfully
• ✅ All core functionality verified (data import, downcast, cleaning)
• ✅ Test suite: 54/54 tests passed
• ✅ Thread requests working
• ✅ Caching functionality working
• ✅ Advanced features (NGS data, PFR data, etc.) working

Backward Compatibility

These changes maintain full backward compatibility:

• NumPy 1.20+ works on Python 3.6.1-3.12 (existing users unaffected)
• Pandas 1.3+ is compatible with existing functionality
• No API changes or breaking modifications

Commits

• 8cfcb6e: Add Python 3.13 support by updating dependencies
• 3252353: Verify Python 3.13 compatibility with comprehensive testing

Closes #122