code: function (x, y, z, w) {
          this.array[0] = x;
          this.array[1] = y;
          this.array[2] = z;
          this.array[3] = w;
          this._dirty = true;
          return this;
      }
docs: Set x, y and z components
  @param  {number}  x
  @param  {number}  y
  @param  {number}  z
  @param  {number}  w
  @return {clay.Quaternion}