ENHANCEMENT needs some tests

[clach04]

Not sure how to validate the run afterwards other than visual inspection 😱

Attached some test samples I've been using in case they are helpful to anyone else:

• test_text_7bit_US-ASCII.txt
• test_text_8bit_latin1.txt
• test_text_8bit_latin15.txt
• test_text_utf8.txt

Problem encodings

• test_text_utf8bom.txt - BOM is displayed as a black box (ideally look for that and remove in initial file IO code). Also see issue Tab character is displayed as a black box if file contains tabs #15
• test_text_utf16le.txt - due to the character opening mode used, and the "for line in file" logic this is not currently supported.
• test_text_utf16be.txt - due to the character opening mode used, and the "for line in file" logic this is not currently supported.