Hyphentitlecase

This adds support for hyphenated words in `Humanize.titlecase`.

eg:

in   : 'by-the-book ultra-book By iTunes'
out : 'By-the-Book Ultra-Book by iTunes'

in   : 'by-the-by is not iTunes-O\'Malley\'s favorite of the new-on-a-book'
out : 'By-the-by Is Not iTunes-O\'Malley\'s Favorite of the New-on-a-Book'

@hijonathan  @b-ash what do you guys think?