Sort Curry results

:fork_and_knife: When viewing watched repositories it isn't always clear that you
actually added the repo. This gives a sort order so you can visually
identify that the repo you just added is on the list.
Is `full_name` ever nil? Because this will blow up if so... [Looking at the code](https://github.com/opscode/supermarket/blob/750acd8d69744be61978f20f7ab4a3a444632a74/app/models/curry/repository.rb#L10-L14), it will return `nil` if either of those values are missing.

Also, you can do this (which I think is cleaner):

```ruby
Curry::Repository.all.sort_by(&:full_name)
```

But we should really do this instead:

```ruby
class Curry::Repository
  include Comparable

  def <=>(other)
    self.full_name <=> other.full_name
  end
end
```

And then just call `.sort`:

```ruby
Curry::Repository.all.sort
```