Don't flatten row array before passing to Hash#[]

Fixes #154

lib/sqlite3/resultset.rb

@@ -86,7 +86,7 @@ def next_hash
       row = @stmt.step
       return nil if @stmt.done?
 
-      Hash[*@stmt.columns.zip(row).flatten]
+      Hash[@stmt.columns.zip(row)]
     end
   end