SKTGraphicView: if the tool starts to create a shape but ends up not creating one (e.g. the user clicks without dragging, creating a 0x0 sized shape), discard the shape which was created with a -discardAllChanges call
Merge pull request #3 from etoile/drawing-avoid-uncommitted-shapes

SKTGraphicView: if the tool starts to create a shape but ends up not cre...