Ensure mb formatString is congruent to standard ucwords() functionality

Currently the mb title case change is not congruent with uc_words() in that it ignores leading numeric characters. This leads to annoying addresses like "555 1St Ave" instead of "555 1st Ave". This small patch fixes that problem and is still unicode safe.
Can you remove the space before the parenthesis ? ie. `mb_regex_encoding('UTF-8');` :)