Second part of Issue 103: tracking of mouse events and new 'rotate' state.  Does not actually rotate the element yet.
Second part of Issue 103: tracking of mouse events and new 'rotate' state.  Does not actually rotate the element yet.

ryanramage/svg-editor,ryanramage/svg-editor,trentmillar/ddp-level-editor,trentmillar/ddp-level-editor,ryanramage/svg-editor,trentmillar/ddp-level-editor