Implementation of secure param for PageUrlAnnotation

There are a few things I am not 100% sure:
- should `$secure` always overwrite the protocol? even if it is not present.
- introduce `$secure` property and getter? Just now I alter the protocol to the current passed value of `$secure`
- comments of the new `$secure` param, quite a lot of information for a single line

Closes #63.
That's the problem. The UrlParser test verifies, that merge function works, but since Normalizer just does "new UrlParser" then we have no idea of knowing whatever the parser is being used or not to produce the final url.

Normalizer here is acting like a factory but assembling a class. And we all know that you can't test if a class was assembled properly. However here we're not assembling a class, but an array which we can assert.

Test for all that url-handling business became unmanageable the time we've created them. Don't know what can be done about that.