As we can only increase verbosity with commandline flags, we
should set the least verbose log level by default.

Tell at least, what level can be set.

Passing in ``None``, should result in no logger changes.

Requires two blank lines between functions.

When we set logging levels, then handlers must support this.

The help page displayed in README should reflect the real help page.

We have to make sure, that `dice_sides` is really used when picking
random values.

While it is nice to have a working plugin example, it looks also a bit
overcomplicated to me. It is better for contributors, if they can find
things (like CLI argument parsing) in one (foreseeable) place and do
not have for things scattered over the whole project.

For plugin documentation we can use the sphinx docs. Or maybe provide
a sample plugin in tests.

This argument makes sense together with ``realdice`` randomsource
and tells how many sides the dice we use have. Six by default.

As we will start to do real things with the options passed in, we need
a real (options) dict also in other tests of `RealDiceRandomSource`.

The RealDiceRandomSource will support own commandline arguments. This
is handled by an own classmethod called `update_argparser` that is
called upon initialization of diceware.

If plugins want to work with their own commandline args, we allow
this by calling their `update_argparser` methods. This has to be a
classmethod, if it exists.

We got API changes, new options, etc. All this will make the
next release a minor one, not a pure bugfix.

Make sure we can use `-v` and `--verbose`.

In config files we normally lookup a ``[diceware]`` section.

For plugins, however, it might be helpful to be able to parse also
other sections. Together with the new `defaults_dict` argument
they could implement their own set of options more easily.

The `diceware.config.get_config_dict()` argument `path_list` was not
properly tested yet. Fix that.

We will not work on passed-in dicts but on copies thereof.

We can now give a custom dict to use for defaults.

This is the first step to make `get_config_dict()` usable also
for plugins.

It is probably not a bad idea to reflect default values in sample
config.