Improve regexp examples
Move service redirect check to redirect function
Support "service" parameter in /logout

The endpoint will continue to support both the "service" and "url"
parameters for now, although CAS 3.0 has dropped the "url"
parameter entirely.
Don't logout user when renew parameter is provided
Add additional CAS 3.0 exceptions
Raise InvalidProxyCallback when validating callback
Extract request parameters within views
Remove alternate custom attribute formats

The CAS 3.0 specification formalizes the format for including these
parameters. As the <cas:attributes> element was already the default
format, continuing to support these other formats increases
complexity and adds potential confusion.
Add a function to convert parameters to bool

This makes the conversion a little more conservative, as it strips
leading/trailing whitespace from the parameter string.
Add a test for displaying the given URL on logout
Use RequestFactory for validation endpoint tests
Remove helper function from views tests
Don't manually build query string for view tests