function getTranslation(out, a) {
    var ax = a[4],
        ay = a[5],
        az = a[6],
        aw = a[7],
        bx = -a[0],
        by = -a[1],
        bz = -a[2],
        bw = a[3];
    out[0] = (ax * bw + aw * bx + ay * bz - az * by) * 2;
    out[1] = (ay * bw + aw * by + az * bx - ax * bz) * 2;
    out[2] = (az * bw + aw * bz + ax * by - ay * bx) * 2;
    return out;
  }
Gets the translation of a normalized dual quat
@param  {vec3} out translation
@param  {ReadonlyQuat2} a Dual Quaternion to be decomposed
@return {vec3} translation