Add a _fillRectMod drawing function that fixes rendering when devicePixelRatio is a fractional number by rendering slightly wider pixels to avoid subpixel rendering in the canvas (see issue #456)
Fixed rounding errors by using min-width and max-width instead of width:100% on safari. Safari is fixed but chrome still has small errors on high resolution screen. Chrome is fine on regular resolution screen. Firefox never had a problem. See issue #341 for old rehash of this issue