Owner model and Visitors controller refactor

Hello @Fibiola, I refactored the Owner model so that you could reuse it for other users or :cat: :smile_cat: :cat2: 
The changes are explained but if you need any help, feel free to ask. Good luck with Rails and keep it up! :squirrel: 

PS. I changed the file indentation to 2 spaces instead of 4 :see_no_evil:, this helps readability and it's a convention amongsts Rubysts!