The temporary wordlists dir must be a string.

With this fixture we can test different wordlist file names without
touching the real wordslists dir. This is important as we cannot say
what files a user stores or removes from that originial directory.

The README is evaluated by standard docutils when released on
pypi.python.org. These do not understand most text roles (like
``:class:``) recognized by `Sphinx`. As a result the README will be
displayed as raw text on PyPI which looks ugly.

There is no need for us to enforce lowercase wordlist names. It
could even confuse people.

We will certainly provide other english lists as well. Therefore
we need something for distinction.

Also this method now handles names instead of language codes.

We will drop the assumption that wordlists are generally organized
by language. There are, for instance, many different language
lists available in english for many different purposes.

Therefore we will support different names for different wordlists,
but the names do not neccessary depend on a language (only).

Make sure it is shown only if neccessary (and not shown otherwise).

Fix real dice input range validation

The new real dice random source now works on a very plain level.