I realize that this makes git blame harder to use on those lines where I'm removing whitespace, but there aren't many whitespace removals outside of comments and blank lines, so that shouldn't be a big issue.

I'd like to do a mass-reformat once rustfmt is stable, so whitespace removal could wait until then. However, the negative impact of removing the trailing whitespace now is small, and it would be really nice for people like @LukeMathWalker and me who have our editors configured to automatically remove trailing whitespace.