Add default delay when delay < 1

Hello,

I have been using gifview for a little while, and I really like it.
However, I initially passed it up because it animated some GIFs at high
speed.

I didn't discover the --min-delay option until today, but it isn't
adequate to cover the following use case:

There are two GIFs:

    a.gif       delay: 0    (looks best at delay=8)
    b.gif       delay: 4

If I use --min-delay 8 to view both a.gif and b.gif, the latter is too
slow, and if I use --min-delay 4 to view both, the former is too fast.

I'd like to use gifview from my file manager, so the .desktop entry for
gifview will contain static command line parameters.

I think it would help the "out of box" usability of gifview to set a
default delay (that can still be raised by min_delay) for GIFs that have
not specified a delay.

The value of 0.08 seconds corresponds to 12.5 FPS which seems to work
quite well empirically.