Collapse job search

this adds the ability to handle collapsed job searches to the ruby api gem.  If collapse is off it will handle everything as it used to. But if collapse is on, it will go down the collapsed path and return a Cb::Models::CollapsedJobResults insted of a Cb::Models::JobResults
This all looks pretty ugly... Here's my next iteration to clean it up a little, though it could use work, I think:
``` ruby
let(:content) do
  {
    ResponseJobSearch: { GroupedJobSearchResults: { SearchResults: { JobSearchResultsGroup: [{
      NumberJobsInGroup: 1,
      GroupingValue: '123321',
      GroupedSearchResults: { JobSearchResult: { } }
    }]}}}
  }
end
```
It's more condensed (which I think it easier to digest), but all those closing brackets on one line looks odd. So maybe it's better to expand it just a little, which just modifies your original by moving brackets around slightly:
``` ruby
let(:content) do
  {
    ResponseJobSearch: {
      GroupedJobSearchResults: {
        SearchResults: {
          JobSearchResultsGroup: [ {
            NumberJobsInGroup: 1,
            GroupingValue: '123321',
            GroupedSearchResults: {
              JobSearchResult: { }
            }
          } ]
        }
      }
    }
  }
end
```
What do you think, Nick?