Fix all lowercase or UPPERCASE case style

Right now the confirm.utils.string.CaseStyle class will translate single words (e.g. FOOBAR, foobar) to f-o-o-b-a-r (and alike) instead of foobar (and alike).
This seems to happen as soon as there's only a single word without a whitespace (FOO BAR becomes foo-bar, but FOOBAR won't).

Fix the library and update the tests.