Allow module-specific theme information to overload "default"
configuration. I.e. it is now possible to have specific prefix or
postfix configurations for different modules. The module name is derived
for each widget from the module (__module__) from which it was
instantiated.
see #23
Add basic drawing of widgets. Each module instance returns a list of
widgets using the widgets() method which is then forwarded to the draw()
method of the configured output.
see #23
