[PATCH] integration test sessions fixture fix

In integration tests when creating a new session with open_session, fixtures would no longer be accessible in the new session.

# works
companies(:test)

open_session do |sess|
  # fixtures not accessible on sess... error
  #sess.companies(:test)
end

The code was broken because the existing session instance adds the fixture methods by checking if the current session responds to the fixture method name with respond_to?, but the fixture methods are private and would return false which would prevent the fixture methods in the new session from being created. Passing true to respond_to? checks private methods as well, which would then return true and then create the fixture access methods in the new session.

The patch should explain the issue more clearly.