Improve calculating method for width of indent line

[Jipok]

They're too fat for me now. Before:

After witch style.guide_width = 1 :

[Jipok]

Perhaps I shouldn't produce unnecessary entities.
@rxi, why did you choose math.ceil(1 * SCALE)? This gives a thickness of 2 pixels already with SCALE == 1.01. Looks too thick even with my SCALE == 1.25
I suggest using math.floor(SCALE + 0.5). Then no additional option is required. The thickness will become 2 pixels after SCALE == 1.5. I checked it looks fine, much better than the current version.