Added the ability to specify template in rendering

Added the ability to specify jrxml template in rendering.

Example:

* app/views/my_controller/action1.jrxml

```ruby

  def action2
    @people = Person.all
    respond_with @people, :template => "my_controller/action1"
  end
```
Template action1.jrxml will be used for request to action2 with pdf format