Drop support for older python versions

[lpetre]

This pull request modernizes the codebase by dropping Python 2 support and updating compatibility to Python 3.8 and above. It removes legacy code and updates CI and packaging metadata to reflect these changes. Additionally, it improves type safety in the Type class.

Python version support and compatibility:

• Dropped support for Python 2 and older Python 3 versions (<=3.7) by removing all __future__.absolute_import imports and updating the minimum required Python version to 3.8 in both setup.py and .travis.yml. Also, added support for Python 3.12 and 3.13 in CI and packaging metadata. [1] [2]

Codebase modernization:

• Removed Python 2-specific workarounds and imports, including try/except blocks for pathlib and all __future__ imports across the codebase. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]

Type safety improvements:

• Updated the Type class in filetype/types/base.py to use Python 3 type annotations for all methods and constructor arguments.