1.3beta1 allows numbers as short as 4 characters as valid

[calebanderson]

With a default country code set '1111' is seen as valid because of this line:
https://github.com/carr/phone/blob/master/lib/phone.rb#L152

And the fact that the only validation around 'number' is that it's 1-8 characters long. This used to be caught because format :really_short would be automatically selected and would try to prepend the area code to the beginning and fail if it was not given.