Testing against Ruby 2.0. Closes #1075.
Merge branch '2.1' of github.com:imathis/octopress into 2.1

* '2.1' of github.com:imathis/octopress:
  Adding a default for comment disabling.
  Make it possible to disable the comments section entirely without having to muck with theme files.
  An update of rretsiem's pull request, for 2.1.
  Removal of apparently unreferenced, dangling method.
  Grand whitespace cleanup.
  Some Jekyll plugins confuse Compass by mucking around with the CWD.
  Allow .md for markdown files.
  Bring over a couple little things from master...
  Simplifying clean task.
  Fix static reference to instance method in Compass' config.
  Remove cruft from Gemfile.lock since rspec is no longer specified in the Gemfile.
  Ignore all generated JS bundles, preview-mode flag, generated _config.yml, and most editor temp files.
  Remove redundant require statement from Rakefile.
  Bump Rack version to leverage security fixes.