[ACTIVEMODEL] Allow passing :index option to MyModel.import

Allows to index the data into a different index:

    Article.import index: 'new_articles'

lib/tire/model/import.rb

@@ -15,6 +15,7 @@ module ClassMethods
 
         def import options={}, &block
           options = { :method => 'paginate' }.update options
+          index   = options[:index] ? Tire::Index.new(options.delete(:index)) : self.index
           index.import klass, options, &block
         end
 

test/unit/model_import_test.rb

@@ -60,7 +60,11 @@ class ImportTest < Test::Unit::TestCase
             # Add 1 to every "document" and return them
             documents.map { |d| d + 1 }
           end
+        end
 
+        should "store the documents in a different index" do
+          Tire::Index.expects(:new).with('new_index').returns( mock('index') { expects(:import) } )
+          ImportModel.import :index => 'new_index'
         end
 
       end