Create an RSS plugin

[reefdog]

We need to create a plugin that will fetch and render content from one of two RSS feeds depending on user authentication status. High-level needs:

• [x] Reads/verifies user authentication status (set by the SSO plugin)
• [x] Fetches and parses appropriate feed based on status
• [x] Displays an index of entries
• [ ] Allows opening/reading individual entries
• [ ] Remembers read items
• [ ] Looks handsome and follows STAT branding guidelines