Allow to add a list of urls that bypass the gateway

[qubird]

At the moment django-perimeter wraps all urls.
It would be useful allowing to specify a list of endpoints/regexes that bypass perimeter.

[hugorodgerbrown]

Originally I had a setting BYPASS_PERIMETER_FUNCTION that would be a lambda that would allow you to interrogate the request object so that you could bypass based on the user, the url, the request etc. This is my preferred option, rather than just URLs.

[stevejalim]

Handled, via BYPASS_PERIMITER_FUNCTION, introduced in 2d3996c