add lexicographic vers scheme

[immqu]

Add a lexicographic versioning scheme which compares versions simply as strings
Addresses #265

[jkowalleck]

a generic versioning scheme that compares versions based on lexicographic order, interpreted as UTF-8.

is there a specification for this, or is it just UTF8 byte compare?

some UTF8 to play with

• NUL -> \x00
• 0 -> \x30
• A -> \x41
• a -> \x61
• Ç -> \xc3\x87 (fourth letter in Turkish alphabet)
• А -> \xd0\x90 (first letter of the Cyrillic alphabet)
• 😃 -> \xf0\x9f\x98\x83

[tschmidtb51]

I would argue that it is strict byte comparison.
@immqu Could you please link the suggested implementation here?

[immqu]

I have updated it using byte comparison now: https://github.com/immqu/univers/blob/lexicographic-scheme/src/univers/versions.py#L149