Added robots.txt, with sitemap link
Category Archive now supports category slugs and titles
For example, in the YAML header set categories like this

categories:
 - awesome [Awesome Posts]
 - news

Octopress will parse out '[Awesome Posts]' and 'news' as the title and display it in
the category list, but the category index urls will be awesome/ and news/

Fixes #902
updated gems, bumping rake to 10.0.3
Fix crash with nil passes
Merge pull request #911 from Keithbsmiley/2.1

Fix crash with nil passes
Add Category List, inspire by https://github.com/alswl/octopress-category-list