Adds the the annotation ID as the class for .annotator-hl spans
adds "active" class to any spans being hovered over.

Problem is that it's greedy...we actually want it to be lazy, so it only highlights the smallest
possible set of highlights that still comprise an entire annotation. Tricky.
Clicking on an anno hl prints a dict of activated annos and their lengths (save point)
Make annotation text container to right of paragraphs and headings.
Prints annotations from each paragraph/heading in its correct display div on right.
Write the annotation pretty, with rounded-corners images and no float bugs.
Mousing over annotation in display panel makes the corresponding hl span pink.
When hovering over multiple highlights, smaller one always gets selected.

To be fixed still: when going from deeper-nested highlight back out into
parent, it doesn't know you're selecting the parent still because the mouseIn
for that has already fired.
Smaller highlight gets activated on hover now, even going from inner to outer nested ones.
Highlights inside active highlights get active color, too.
If two hovered-on highlights have same length, highlights both their annotation on righthand pane.
Active highlight is shown on scrollbar.
"Collapsed" class removes annotation texts, just shows author imgs.
Expand/collapse works on individual paragraphs, and a link to do all of 'em.