refactor: Modularized ASCII into separate files.

[jordanbrotherton]

Resolves #66

ASCII files are now managed in separate files, allowing for a more modular, conflict-free workflow.

ASCII Format

ascii.txt is removed in favor of an ascii folder, which contains individual files containing each image.
The file's first line can contain a 6 character code which handles the unique cases that were previously hardcoded in the get_graphics method.

• GAMEBD: Only for the gameboard image's encoding.
• CENTER: Centers the contents of the file to a default terminal's width (75)
• NWLCUT: Removes all newlines (\n) in the image
• NSTRIP: Performs a strip() to the image
• LSTRIP: Performs an lstrip() to the image
• RSTRIP: Performs an rstrip() to the image