Allow setting the time scale significantly higher than 4

[aaronfranke]

$ gource --time-scale 20
gource: time-scale outside of range 0.0 - 4.0
Try 'gource --help' for more information.

I wish to make the time scale significantly faster than the current maximum of 4, my desired time scale is 20. I've tried recording at a time scale of 4 and then speeding up the recording, but this doesn't look right due to the animations being sped up.

Why is there a hard limit placed at 4? Are there technical problems with faster time scales?