Cookbook Show UI Integration:
- Minor restructure to page to allow for full bleed columns
- Equal height columns on show page
- Format pre and code tags for command line examples
- Format cookbook heading and sidebar content
- Underscore category names in category nav
- Add template views for kaminari pagination
- Format pagination against Foundation conventions
- Restyle breadcrumbs
- Add previous page chevron next to cookbook name
- Separate cookbook show into partials for reuse for cookbook version
  show
Merge pull request #224 from opscode/show-cookbook-ui-integration

Cookbook Show UI Integration
Add an atom feed for cookbook versions to the cookbook show page
Merge pull request #234 from opscode/cookbook-versions-atom-feed

Cookbook versions atom feed
Make cookbook url validation stricter.

Use validate_url for Cookbook URL validations to ensure that no nonsense is
present.
Implement most downloaded/followed filters

Implement most downloaded/followed filters from cookbooks index. Also
add top three most downloaded/followed to cookbooks directory.
Merge pull request #245 from opscode/sort_by_downloaded_followed

Implement most downloaded/followed filters
Merge pull request #243 from opscode/strict_url_validations

Make cookbook url validation stricter.
Add category class to the cookbook partial.

This colors the cookbook partial based on their category.
Merge pull request #250 from opscode/cookbook_category_color

Add category class to the cookbook partial.
Replace Devise authentication with ChefOAuth2.

[ci skip]

This is not yet complete, as oc-id is not deployed in production and the
omniauth strategy is not open source (Travis CI builds cannot pass).

This replaces Devise (email/password) authentication with Omniauth
authentication. Supermarket uses oc-id, a Chef service, as the provider for
authentication. This means that for a user to sign up and/or sign in to
Supermarket they must create a Chef Server account, as they currently do. This
however removes the duplication of records and simplifies the communication
between the community site and Chef Server for authentication when sharing
cookbooks.

Notes:

* Remove omniauth-twitter because it is no longer being used
* Store chef_oauth2 public key on Users.
Update the chef_oauth2 extractor to be correct.
Adjust the cookbook follow spec.
Remove notnot from the signed_in? method.