Added 2.66 compatibility

The default output path is now found from the user preferences
instead of the scene render path.  This was added because Blender
2.66 restricts access to bpy.context while registering and
unregistering modules as noted in http://wiki.blender.org/
index.php/Dev:Ref/Release_Notes/2.66/Addons#Restricted_Context.
Merge pull request #1 from dergemkr/master

Added 2.66 compatibility.

Merged in! Thanks for the update!