Can rewriter interface be improved? #162

What do the Boolean flags include_whitespace and include_comments exactly mean?
E.g., if you replace with include_whitespace does the replacement text then start on the previous line (as a new line character is also a white space)?

Can we get rid of extended_end_offset?

Can we come up with a solution that works for all language - yet still support unique requirements - like correct indentation by Python?
E.g., could we specify better using the concepts of line and indentation?