use #get_solr_response_for_doc_id instead of SolrDocument.find, so the finder respects the blacklight solr configuration
use Blacklight::SolrResponse and ::SolrDocument in Spotlight::Search to take advantage of the error handling and consistency those APIs present; fixes #466
Merge pull request #468 from sul-dlss/issue-467

use #get_solr_response_for_doc_id instead of SolrDocument.find, so the f...