Fix cookbook platform and dependency access scope

Accessing these relations through a has_one relation results in
displaying all SupportedPlatform and CookbookDependency models
associated with _any_ version of the cookbook.

This feels like it could be a Rails bug, but for the time being, we can
fix it by adding these two simple methods to Cookbook
Handle no specified cookbook supported platforms.

In the UI, if there are no supported platforms specified for a cookbook, let the
user know.

This displays an icon and tooltip message on the cookbook partial and cookbook show.
Merge pull request #301 from opscode/fix-cookbook-dependency-and-platform-query-scope

Fix cookbook platform and dependency access scope
Merge pull request #302 from opscode/handle_no_cookbook_supported_platforms

Handle no specified cookbook supported platforms.
Formats the filter by options on cookbook search results.