Non-existing character in an alphabet

[tigertv]

Conclusions from #2:
Handle exceptions when a character doesn't exist in an alphabet.
A solution would be either to show an error message or remove non-existing characters from message.

[ZetaTwo]

At least for Caesar it would be good to be able to just leave the character in place.

[tigertv]

Hi @ZetaTwo !

... just leave the character in place.

Developer decides how to handle the situation, he uses either a 'try-catch' or correct input(only characters from alphabet).
Also developer can use the wrappers 'SaveAll' and 'RemoveNonAlphabet' which save and remove non-alphabet characters correspondingly:

secretpy/examples/caesar.py

Lines 42 to 48 in b87b822

	plaintext = "I love non-alphabet characters. These are : ^,&@$~(*;?&#. That's it!"
	cm = SaveAll(cm0)
	encdec(cm, plaintext)
	plaintext = "I don't love non-alphabet characters. I will remove all of them: ^,&@$~(*;?&#. Great!"
	cm = RemoveNonAlphabet(cm0)
	encdec(cm, plaintext)

[ZetaTwo]

Also developer can use the wrappers 'SaveAll' and 'RemoveAll'

Perfect. This was exactly what I was looking for. Thank you.

[tigertv]

You are welcome!