title: jssor fixed pixel dimensions requirement
body: <p>What is the rational behind jssor to require all fixed dimensions in pixel? This could be clearly more user friendly if jssor library gets parent dimensions from available JS api. Often we would like something to be relative to the parent without dealing with scaling and such. Outer and inner container report problems if any value is not in pixels. This is really the only and biggest issue for me in otherwise great library. It should be more responsive by nature, without manual scaling methods.</p>