Integrate Semiotic Mark

This removes the semiotic-mark dependency and as a result the d3-transition dependency and removes the most ambitious features of Semiotic Mark:

Animation: Semiotic Mark used to self-animate, and even go so far as to honor custom tweens for things like arcs. It no longer self-animates. It might come back in a more thoughtful way.
Drag-And-Drop: Semiotic Mark used to have a robust drag-and-drop functionality allowing you to move a mark and even tell when it was dragging over other marks. This is gone and likely won't come back.

nteract / semiotic