Is there a way like history.back() and has 'slide-in' ?
I modified push.js where ：
transition = direction === 'back' ? transitionMap[transitionFromObj.transition] : ransitionFromObj.transition
to：
 if(direction === 'back' && transitionFromObj.transition === 'slide-in') {
        transition = 'slide-out';
    } else if(direction === 'back' && transitionFromObj.transition === 'slide-out') {
        transition = 'slide-in';
    } else {
    transition = transitionFromObj.transition;
    }
and 
var transitionMap  = {
    'slide-out'  : 'slide-out',
    'slide-in' : 'slide-in',
    'fade'     : 'fade'
  };
Is it ok?
