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.

I tried out this change [on a local install](https://github.com/JasonBarnabe/greasyfork/wiki/Running-Greasy-Fork-locally) with test data, and everything still seems to work:

![screenshot of working refactored Applies To in Greasy Fork](https://cloud.githubusercontent.com/assets/79168/3936836/bd999abc-24a6-11e4-9007-47e162b3ff8d.png)