Added a Slicing typeclass.
Got rid of StringShouldWrapper and ResultOfNotWordForString. Merged these
into Any, and just added evidence that T is String. Had to make the Should/MustVerb
traits used by WordSpec, FlatSpec, etc., have an implicit conversion with the same
signature as the one that converts T to AnyShouldWrapper.
Got rid of overloaded aall/every/etc methods that did the String element. Now
it should work with dynamic proxies and should be possible to do the
inspector shorthands generalization noew.
Made Slicing private.