Refactor “Applies to” list display on script#show page

Moved complicated Ruby code from the view into a helper, then split that helper in multiple, easier-to-understand methods.

Removed unnecessary `h()` calls – Rails automatically escapes unescaped text. Also changed manual HTML building with `html_safe` to use `content_tag`.

Changed HTML representation of the list – made the list an actual `<ul>`, with CSS to make it display as comma-separated.
Merge pull request #232 from roryokane/refactor-applies-to-list

Refactor “Applies to” list display on script#show page