Extract render_method

This extracts the inner part of method_document and renders a single
method.
Extract add_extension_modules_single

This was extracted from add_extension_modules and renders a single
extension module.
Extract add_extension_modules_multiple

This was extracted from add_extension_modules and renders more than one
included module.
Extract render_class

This renders a single class
Extract render_method_arguments

This renders the argument lists for a method.
Extract render_method_superclass
Extract render_method_comment
Extract complete_klass

This is pretty ugly due to all the arguments.
Extract complete_method

Like complete_klass, this is also a bit ugly due to all the arguments
Align method arguments