Version bump to 2.6
New transformSingleItemLists function

Unordered list elements containing a single list item element are now
effectively unwrapped. This avoids the strange single bullet layout that
occurs as a result of other cleanup operations.
Minor comment changes
Minor changes

Annotate more elements. Changed some comments. Restrict which elements
are affected by attribute bias. Added some more blacklisted selectors.
Refactored how image dimensions are set

Mostly this moves around some of the responsibility between caller and
callee. The caller now gets the images array and the callee now only
handles a single image at a time.