support for CDATA content
If type specified CDATA content won't be escaped. This makes it easier
for RSS publishers and readers.
Also adheres CDATA recommendation at http://www.rssboard.org/rss-profile#element-channel-item-description
Merge branch 'master' of https://github.com/shon/python-feedgen

This merges in a pull request by Shekhar, adding support for CDATA
content:

---

If type specified CDATA content won't be escaped. This makes it easier
for RSS publishers and readers. Also adheres CDATA recommendation at
http://www.rssboard.org/rss-profile#element-channel-item-description

---

Signed-off-by: Lars Kiesow <lkiesow@uos.de>