[FAILING TESTS] lines with trailing spaces

[soenkehahn]

I created this PR instead of opening an issue, because I thought it would be easier to describe and understand. So this is not a PR submitted for merging, but a bug report.

When endent encounters spliced in text that is indented relative to other text in the template string, it inserts indentation on any newlines that appear in the spliced in text. (Which is great!) However when the spliced in text contains two (or more) consecutive newline characters, this means that the text that endent yields contains lines that contain only spaces. As far as I can tell, this is (almost?) never the desired behavior. So I think endent should not insert indentation spaces on empty lines.