The cloudformation module argument spec should match the documentation.  

The cloudformation module argument spec should match the documentation so that template_parameters is a required argument.

The [documentation for the module](https://github.com/ansible/ansible/blob/devel/library/cloud/cloudformation#L41) states that `template_parameters` is required, but [the implementation](https://github.com/ansible/ansible/blob/devel/library/cloud/cloudformation#L162) says otherwise.  If a playbook uses the cloudformation module without the `template_parameters` argument, the following error may occur:
   
    File ".../cloudformation", line 168, in main
    template_parameters_tup = [(k, v) for k, v in template_parameters.items()]
    AttributeError: 'NoneType' object has no attribute 'items'