Added `toTitleCase` & `slugify` functions to `FlxStringUtil` (#2670)
Added `toTitleCase` & `slugify` functions to `FlxStringUtil` (#2670)

* Added `toTitleCase` & `slugify` functions to `FlxStringUtil`

Added a couple of simple helper functions to `FlxStringUtil`:
`toTitleCase` will turn something like `"a tale of two cities, pt ii" into: `"A Tale of Two Cities, Part II"`
and `slugify` which will turn a string into a 'slug': Example: `"A Tale of Two Cities, Part II"` becomes `"a_tale_of_two_cities__part_ii"`

* renamed `slugify`

Renamed the new function from `slugify` to `toUnderscoreCase` as requested.
HaxeFlixel/flixel