Extract category_link filter from category_generator.rb plugin

Allows category_link to be used as a filter to display a link to
any category.
Added robots.txt, with sitemap link
Example repo URL - see Github issue 516
Updated Github API to V3.

Github API V2 has been removed.  The response data format also changed.
Updated Github API to V3.

Github API V2 has been removed.  The response data format also changed.
Merge pull request #666 from nathanl/example_repo_url

Example repo URL - see Github issue 516
Updated gems and rubies to 1.9.3
Merge branch 'master' of github.com:imathis/octopress
Fix for issue #622

The filters bundled with Octopress are not applied to files ending in 
`.md`, because the match in octopress_filters.rb does not match `.md`.
Merge pull request #706 from Confusion/patch-1

Fix for issue #622
initial commit
initial _config.yml
improved starting point
added compass, added some basic stylesheets
paramaterized layout and page files
added rss metadata to layouts
paramaterized feed, rsync deployment, and unified layouts
added auto generated copyright to footer as well as credit for Jekyll and Octopress
page titles are now formatted "Title - Blog Title"
updated typography, added typography debugging page