Correct max_length for UserAndProfileForm

Django's User model specifies a max_length of 30 for first_name and last_name fields.

https://github.com/django/django/blob/stable/1.4.x/django/contrib/auth/models.py#L235
Merge pull request #1204 from tangentlabs/issue/customer_form_allows_too_many_characters

Correct max_length for UserAndProfileForm