koajs/koa — pull request #291 by jonathanong (2014-06-05 23:05:39+00:00)
Title: remove response.append(), use vary module

basically, `response.append()` was only really used for `vary()` and it doesn't really have a use-case for other headers. so why not just remove it? now we've got the [vary](https://github.com/expressjs/vary) module.