ADFGVX ignores numbers

[alpire]

Testcase:

In [1]: from pycipher import ADFGVX

In [2]: ADFGVX().encipher('1')                                                                                                                                                                            
Out[2]: ''

I would expect the ciphertext to not be empty, as ADFGVX supports numbers.

I believe the issue was introduced here and here. Without the filter argument, remove_punctuation filters out any numbers.