escaping cdata?

Great module!

I'm converting kml which contains cdata to geojson and saving that back to kml.  In the process, the cdata tags are lost, which makes the xml invalid.  I resolved this issue by changing the description function to wrap the description in a cdata tag.  I'd try to push it, but I'm not sure if it would goof anything up.

Anywho, thanks!
