Grid mode shifts fonts to 0.5px, causing blurred fonts

[mlesin]

It happens eventually and depends from target width. I suppose it's because of calculation of _rowMargin in initializeData() func - there is a division by two, frequently causing values like 38.5 or so. It should be rounded, i think. Not sure where to do it better - in initializeData() func or in positionItems() func, right before pushing values into css's translate3d().
I found it in dart version but looks like JS version should have the same issue.