Fix allow hex input formatting

[makinako]

Thanks for this simple and excellent tool! I often use it for manually checking cryptographic test vectors in algorithm development and often when dealing with complicated hex input structure, I break it up to make it more human readable.
This PR just allows any kind of whitespace and the most common hex delimeters to be used in the input without an error or modification to the output calculation.

The following formatted inputs (and any combination of formatting characters) will all produce the same output:

• 112233
• 11 22 33 (Space)
• 11 22 33 (Tabs)
• 11.22.33 (Period)
• 11:22:33 (Colon)
• 11\22\33 (Backslash)
• 11/22/33 (Forwardslash)
• 11-22-33 (Hyphen)
• 11_22_33 (Underscore)

and CR, LF or CRLF:

11
22
33

Thanks again,
Kim

[emn178]

Thanks for the PR!

There is now a new optional mode for hex input formatting. The default hex mode remains strict, while the new mode allows formatted hex input by ignoring whitespace/separators. This should cover the use case here without changing the existing default behavior.