Fix default Rake task and tweak task descriptions.
Add support for photoset posts.
Make Git ignore all CSS and HTML files.
Fiddle about with main content markup and styles.

  - Implement a basic grid system for main content with support for
    sidebar content in the future.
  - Change some of the layout CSS rules to module CSS rules.
  - Tweak page body margins to make the new stuff fit in.
  - Purge some tabs along the way.
Add hacky responsive design stuff.