Support for hiding comments on Index pages

The proposed solution uses a custom variable on each post's [YAML front matter](https://github.com/mojombo/jekyll/wiki/YAML-Front-Matter) block which is [passed to a JavaScript function](https://github.com/ploeh/ploeh.github.com/pull/5/files#L205R17) using the Liquid templating system.

The Web feeds remain intact.