Fix the issue with a single object vs array being returned

If you use load: true when the search would return a single object it raises the error
NoMethodError:
       undefined method `detect' for #<--elastic search persistance model-->

This has been fixed before but it must have been lost when the code was refactored.
See https://github.com/karmi/tire/pull/353

Original issue:
http://stackoverflow.com/questions/10592005/tire-gem-undefined-method-detect