The correct default options for sudo_flags can be found at: https://github.com/ansible/ansible/blob/devel/lib/ansible/constants.py#L181
Slightly alter explanation of '-H' so as not to confuse it with -E, --preserve-env (which preserves existing environment variables).
When adding the two other options, include short explanations of those options.
Add note about '-n', which did not appear in 1.x I believe, and which bit me.
