Multibyte first character

[atrakowski]

Problem

There are names starting with an Umlaut or some other multibyte character, e.g. Öykü Çelik. Currently they are incorrectly lowercased, because the Regexp for upcasing the first letter only matches /\b\w/ i.e. /\b[a-zA-Z0-9_]/.

NameCase("Öykü Çelik", lazy: false) # => "öykü çelik" (expected "Öykü Çelik")
NameCase("Öykü Çelik".downcase) # => "öykü çelik" (expected "Öykü Çelik")

Fix

Use a Regexp based on Unicode properties like /\b\p{Word}/. With that the tests still pass, including a new test for a name starting with a multibyte character.

FYI: There are two commits. The first one is the fix itself, in the second commit I've replaced all remaining occurrences of \w with \p{Word}. If the latter is too much of a change, I can easily undo it.