Fix internal server errors in get_translated_url for function-based views with class kwargs
Improve TranslatableSlugMixin to abort redirect on resolved fallback URLs

This avoids depending on render_to_response() to return the actual
response. Instead, an exception is raised to break out, and let
dispatch() return the right redirect response.
Added unit tests for URL handling.

- resolving translated URLs
- translating URLs to other languages
- testing TranslatableSlugMixin