stpl: set yrange [0.1:] to allow logarithmic plots

Should've had its own option, it shouldn't be the default. But I'm too
lazy to fiddle around with Getopt::Std, it should work in all my use
cases. Will update the script to some modern standard at some point in
time anyway.

0143f3f6-d5c6-11e2-b7b3-001f3b596ec9