Fixes missing url escaping on redirect.
- Fixes #110.
- Updated test to use escaped query strings, reveiling problem.
- Updated owin handler in the same way, although test is not failing (Cheating, I know).
- Reason for bug is that Uri.ToString() will return an *unescaped* string, even if original string was escaped.
- They mystery is how it has even worked at all with the old code.