Inline implementations of FromAscii(fromAscii)
Refactoring structure of Text.Pwgen.FromAscii

It now follows common pattern of using Class module for the class
definition along with basic instances and separate instance modules for
other specific instances.
Generic predicates for characters

* Predicates use FromAscii class to abstract from concrete
  implementation.
* Additional dependency on not-found package.
Bumping version to 0.2.0.0