Switch Capybara check in after hook to check for class inclusion.

Using  initializes a new Capybara::Session, which, aside from being expensive,
can cause issues on non-Capybara tests.

lib/capybara-screenshot/rspec.rb

@@ -47,7 +47,7 @@ class << self
         attr_accessor :add_link_to_screenshot_for_failed_examples
 
         def after_failed_example(example)
-          if Capybara.page.respond_to?(:save_page) # Capybara DSL method has been included for a feature we can snapshot
+          if example.example_group.include?(Capybara::DSL) # Capybara DSL method has been included for a feature we can snapshot
             Capybara.using_session(Capybara::Screenshot.final_session_name) do
               if Capybara.page.current_url != '' && Capybara::Screenshot.autosave_on_failure && example.exception
                 filename_prefix = Capybara::Screenshot.filename_prefix_for(:rspec, example)