fixed layout two-page spread, zoom calculation when different heights

[danielweck]

To be checked.

Code references:

https://github.com/readium/readium-shared-js/blob/develop/js/views/fixed_view.js#L424

else if(_leftPageView.isDisplaying() && _rightPageView.isDisplaying()) {
            if(_leftPageView.meta_height() == _rightPageView.meta_height()) {
                _contentMetaSize.width = _leftPageView.meta_width() + _rightPageView.meta_width();
                _contentMetaSize.height = _leftPageView.meta_height();
                _contentMetaSize.separatorPosition = _leftPageView.meta_width();
            }
            else {
                //normalize by height
                _contentMetaSize.width = _leftPageView.meta_width() + _rightPageView.meta_width() * (_leftPageView.meta_height() / _rightPageView.meta_height());
                _contentMetaSize.height = _leftPageView.meta_height();
                _contentMetaSize.separatorPosition = _leftPageView.meta_width();
            }
        }

https://github.com/readium/readium-shared-js/blob/develop/js/views/fixed_view.js#L320

 var horScale = potentialContentSize.width / _contentMetaSize.width;
        var verScale = potentialContentSize.height / _contentMetaSize.height;

        var scale;
        if (_zoom.style == 'fit-width'){
            scale = horScale;
        }
        else if (_zoom.style == 'fit-height'){
            scale = verScale;
        }
        else if (_zoom.style == 'user'){
            scale = _zoom.scale;
        }
        else{
            scale = Math.min(horScale, verScale);
        }

[danielweck]

Screenshots: