Add more style options to graphie.addCircleGraph

Summary:
Adds normal/highlight style options for both the circle and the center
point in graphie.addCircleGraph()

Test Plan:
 * Make an interactive-graph with a circle in Perseus
 * Verify that the circle is blue, but highlights orange
   on hover
 * Orange/orange used in a new Transformer commit
 * There's a known bug related to stroke-dasharray :(

Reviewers: alex

Reviewed By: alex

CC: alpert

Differential Revision: http://phabricator.khanacademy.org/D5570