Fix MX curp field

[quevon24]

Correct regex to validate MX CURP is:

curp_re = (r'^[A-Z][AEIOUX][A-Z]{2}%s[HM]%s%s{3}[0-9A-Z]\d$' %
                   (DATE_RE, states_re, consonants_re))

It needs an X because the second character is the first vowel of the first last name(surname), in the case that there is no vowel, CURP comes with an X, e.g: For example mayan last name 'OY'() second char is a consonant, not vowel, so the the beginning of the curp it's OX and it's not valid with actual regex.

[benkonrath]

Thanks for the PR. A couple of points:

• Could you add an example of a valid CURP with an X to the CURP test? This helps to double check the fix.
• We also need an entry to the change log for this bug fix.
• [optional] You can add you name to the authors file if you want.

Thanks again for the fix!

[quevon24]

Thanks, I commited the new changes with what you ask for. I added an example to test_MXCURPField and the new entry on changelog.

And thanks for this incredible package. 👍

[benkonrath]

Thanks! :hand: (high five)