#17 Add css markup for literalblock.

[Ammon Riley]

I found that example code, and other literal blocks didn't stand out well enough in generated documentation. You can fix this by using reStructuredText, but not if you want to stick to epydoc's simpler markup.

This patch copies all of the doctest css entries to new literalblock entries, so that literalblocks have the same pretty blue box as doctest sections do.

[Ammon Riley]

Addition of literalblock formatting.