Move functionality to StringHandler class.
Add vertical tab as delimiter for ::ucWords()
Extend functionality.

Add functionality to trim strings and remove duplicate characters.
Fix bugs, extend functionality, refactor.

* Fix: Case insensitive check performed if case sensitive check requested.
* Check input parameters for validity.
* Left the needle be an array in ::contains().
* Rename ::diff() to ::getDiff().
* Rename ::lines() to ::asLines().
Extend functionality.

Add functionality to check if a haystack string contains multiple needles.