Introduce "accuracy" option while reducing performance improves fitting precision.

[rikschennink]

Currently, if the distance between the text width and the container width is very small the re-scale is sometimes off by a couple pixels. Increasing the distance on purpose will result in an additional reflow (thus lowering performance) but would increase fitting accuracy.

[KoalaBear84]

This would be great. As I now have this problem of it resizing even 'tick' of update with only 0.12px font-size or so. So it gets a little bigger, and the next time a little smaller, and so on.