Weblogin

- Adds support for LADOK's test system.
- Improves error messages.

**Full Changelog**: https://github.com/dbosk/weblogin/compare/v1.3...v1.4

Improves detecting failed authentication. Adds tests for this feature too.

**Full Changelog**: https://github.com/dbosk/weblogin/compare/v1.2...v1.3

Makes ladok.SSOlogin attempt to log in at the university authentication service
too. Allows us to specify (and extract) the variables needed.

What's Changed
* Generalize LADOK login, with variable discovery by dbosk in https://github.com/dbosk/weblogin/pull/4


**Full Changelog**: https://github.com/dbosk/weblogin/compare/v1.1...v1.2

What's Changed
* Add LADOK login by dbosk in https://github.com/dbosk/weblogin/pull/3


**Full Changelog**: https://github.com/dbosk/weblogin/compare/v1.0...v1.1

What's Changed
* Redesign AutologinSession by dbosk in https://github.com/dbosk/weblogin/pull/2

**Full Changelog**: https://github.com/dbosk/weblogin/compare/v0.4...v1.0

**Full Changelog**: https://github.com/dbosk/weblogin/compare/v0.3...v0.4