Feed integration with CIT website

Added a courses#cit_feed action to support integration with the main CIT
website (currently managed with Expression Engine (EE)).  We'll expose
several feed formats, and then we can see which format works best with
EE.  This is the JSON format feed.
Added RSS and Atom feeds

Usually you don't need both an RSS and Atom feed, but I went ahead and
implemented both formats, so we can see if Expression Engine likes one
better than the other.
Only send the :title from a Course

Trying to keep things simple and streamlined, so decided not to send
both the :title and :short_title.  If we need the :short_title, then we
can adjust it later.
CSV feed for workshop courses

Uses the 'csv' ruby library to generate CSV
Added upcoming course feed; REFACTOR!

Added feeds for the upcoming courses.  With the upcoming feed being
driven by the date/time for a section part, it didn't really make sense
to me to keep it in the courses controller, kinda breaks the REST
principle.  So pulling the feed actions out into a feed controller made
more sense, with feed#index and feed#upcoming actions.

This leaves the course controller alone, and keeps things DRY and tidy.
Add :items parameter to feed#upcoming action

Make the number of upcoming items variable, set by the :items parameter.
If no :items param is present, it'll default to 5.  Figured this would
give some flexibility with the integration and allow tweaking from the
client side w/o needing backend changes.
add basic feed controller tests
Merge pull request #4 from cit-jmu/cit_feeds

Feed integration with CIT website