- Change `drag.canDrag` to `drag.enabled`
- Track when dragging ends to reset the delta measure point
- Remove dragstart event which won't fire in the host

- consistent use of font family variables
- consistent use of variable-ized $white color
- make use of the heading variables
- make .nav-tabs subsume tabbox mixin
- drop underlines from links (let's try it)
- unify .content and media queries
- extract noise class

Fixes #387

proof of concept only. for localwiki.

Needed a stop marker after the threshold, so that the area above
the top bucket (under the toolbar) doesn't show as having annotations.

Merging buckets is now done in the initial pass. The entire heatmap
is calculated in two passes. The first creates the buckets while the
second counts the replies.

Use `interpolateHcl` because that's hella easy.

I was avoiding expanding buckets beyond the bounds of their
annotations' locations by preventing merging with empty buckets.
However, empty buckets should totally merge with empty buckets.

- Assign the temp id in 'beforeAnnotationCreated'
- Thread annotations after loading so that they have a `thread`
  property.
- Don't reference threading directly in `setupAnnotation`, instead
  let's leave that to when the reply is created. We need better
  events in Annotator for the Threading plugin to be fully automatic.

fixes #158

After this we should be able to remove some references to threading
and instead use the data in the annotation.