fix epydoc warnings

literal blocks in epydoc syntax are defined by double colon on end of
line, so fir few intances when they are not prefixed by it or the
following text is not properly formatted (indented)
add test for epydoc to test-dev target

Patches should not only pass unit tests but also have proper
documentation...
add docs/ directory to .gitignore

since we don't push documentation changes to git, don't include it in
changed files as reported by git
add graphs to generated documentation

make the documentation more readable by adding graphs of class
inheritance
Merge pull request #30 from tomato42/epydoc-fixes

epydoc related fixes (Hubert Kario)