code: function ( degree ) {
              if ( $B.isNumber(degree) ) {
                  if ( !this._disabed ) {
                      var clockwise = ( this._degree < degree ),
                          grow = this._getGrow( this._degree, degree, clockwise );
      
                      degree = this._correctDegree( degree );
      
                      var center = this._centerPoint,
                          point = this._getPoint( degree, center );
      
                      this._dispatch( 'rotation', undefined, degree, point, point, center, grow );
                  }
                  return this;
              } else {
                  return this._degree;
              }
          }
docs: ===============	Public Methods =============== // 
  각도설정 및 반환
  @param	{Number}	degree
  @return	{RotationEvent, Number}