Fixing a bug in the `comparable` built-in.
Returning the wrong type of node from `saturation` and `lightness`.
Fixing a bug in the expansion of selector groups with back-refs.
'Nuther tweak to the backref-in-selector-group fix. Not quite done yet.
Finishing up the backref-in-selector-groups bugfix.
Merge git://github.com/hcatlin/libsass