Bump jekyll-feed from 0.15.1 to 0.16.0

Bumps [jekyll-feed](https://github.com/jekyll/jekyll-feed) from 0.15.1 to 0.16.0.
- [Release notes](https://github.com/jekyll/jekyll-feed/releases)
- [Changelog](https://github.com/jekyll/jekyll-feed/blob/master/History.markdown)
- [Commits](https://github.com/jekyll/jekyll-feed/compare/v0.15.1...v0.16.0)