Tweaked Matchers Scaladoc. Made implicit in PrettyMethods a PrettyConfig to get the
Any => String conversion non-implicit, because that can be accidentally applied
all over the place.
Added a test showing a composition of two Prettifiers. Already worked.
Will wait for more actual use cases before adding more.
Tweaked Matcher Scaladoc. Added a commented out test in ShouldBeSymbolSpec.