setup: Move pseudo-docstring to a proper comment.

A string statement is not a docstring if it doesn't occur right at the top
of modules, functions, class definitions etc.

This patch fixes it.

Signed-off-by: Rogério Brito <rbrito@ime.usp.br>
setup: cosmetics: Add/remove some whitespace for readability.

This also fixes some long lines.

Signed-off-by: Rogério Brito <rbrito@ime.usp.br>
setup: PEP-8 fixes.

Signed-off-by: Rogério Brito <rbrito@ime.usp.br>