Updated annoucement feed to use the site's description, and not RITlug's

[xforever1313]

I noticed the Announcements RSS feed used RITlug's description, and not FOSS@RIT's description.

With this update, the tag will now use the one in the config.yml file. It will look something like this:

<description>
Center of gravity for Free and Open Source Software at the Rochester Institute of Technology. Learn about open source activities and academia at RIT.
</description>