Separate titleize and titlecase behavior

This commit addresses #3662

* Titlecase falls in line with ruby's upcase and downcase. It
    capitalizes each word in the string.
* Titleize retains the old behavior. It removes punctuation, replaces
    e.g :: with /, _ with ' ', etc.

One doubt I have is whether "MAN WITHOUT A PAST" should be titlecased to "Man Without A Past" or should be left as it is. I lean to the first version (transforming it) but wanted to hear some feedback first. It is not yet implemented so it should be an extra commit.