@Override
    public void onAnimationStart(Animator animation) {
        mCurrentFraction = 0;
        if (mCardAnimationListener != null) {
            mCardAnimationListener.onAnimationStart();
        }
    }
bring card to front by Z index, the card with smaller Z index is in front of the card with
bigger Z index
infinite-cards/src/main/java/com/bakerj/infinitecards/CardAnimationHelper.java