Show message if YTS request fails

Now displays an error message when a request for the YTS API fails. eg: timeout, no internet etc.
Show the Loading spinner when changing categories

Now displays the loading spinner when searching or choosing a new genre. This provides more consistent UX and lets the user know something is actually happening.
Don't show loader on scroll

Fixes the loader so it doesn't show when scrolling down the page. This may be wanted behavior in the future tho...?