Revisions

- Great first project Nix, I am really happy with it; 
- I can see from your code that you fully understand CRUD and your CSS is excellent!
- I have made a few revisions, use the link_to helper instead of anchor tags, there are a couple of places where you need to change this; 
- You should avoid using global variables at all costs, I removed the one you had in the tasks controller create action; 
- It would be nice if you changed the button_to helper tag to a form_tag, then you can pass the id in a hidden field in the form rather than having it in the URL; 
- You have 4 different routes to view: all tasks, tasks sorted by category, all archived tasks & archived tasks by category - they all use a very similar views; 
- You can see I have started refactoring your code to use the same route for the index_by_category, this significantly reduces the amount of code you have to write; 
- Have a go at refactoring your code further to use the same route for archived tasks as well;