Fix the URL system

The URL system is very buggy.

Creating a new post with the following title can screw up the site.

"test"

or

it's

We need to either make sure input validation is done everywhere (create a helper function) or change how we handle URLs so no helper function/input validation is needed.

See: https://projects.sucs.org/projects/sucs-site/ticket/62

https://projects.sucs.org/projects/sucs-site/ticket/36

I should say without breaking existing URLs, but If an elegant solution comes up then I suppose we can vote on it.