Adds CSS rules for grabbing and rotating, bring grab point closer
Adds CSS rules for grabbing and rotating, bring grab point closer

Summary:
Some students are confused about how to rotate the protractor. It
looks like the grabbable point is a little outside the range of the
arrow, and hovering over the arrow doesn't give any kind of
indication that an action can be taken. This change brings the
grabbable point a bit closer to the arrow and gives a visual cue
that a different action can be taken.

Test Plan: * Tested in browser

Reviewers: emily

Reviewed By: emily

Subscribers: jared

Differential Revision: https://phabricator.khanacademy.org/D36885

learningequality/perseus,ariabuckles/perseus,ariabuckles/perseus,ariabuckles/perseus,ariabuckles/perseus,learningequality/perseus