Most classes are missing docstrings describing behavior

[jtgans]

Given that over half of the g13gui module is expected to be used by third-party applications (bitwidgets, applet, observer), we should at minimum have the following things documented:

• Every public method and object in each module should at least have a one line description of what it does, what the arguments it takes are, and what it returns
• Unit test case methods should have a short docstring explaining what they test, and how.