Patches from Patrick Michaud:

Patches from Patrick Michaud:

Ok, I've fixed the y-tic error - that was an embarrassing display of math
:(  I'm gonna work on the size issue now, and if I still have time, work
on using Chart::Math::Axis.

ok, i implemented autoscaling of the graph area, and removed a bunch of
cruft around graph size.

Ok, that auto-y-scaling is pretty nice.  Here's a diff that uses it, if
someone calls use_automatic_axis(), or if automatic_axis => 1 is in the
style.  Next I'm going to get some horizontal grid-lines going.

I added somewhat cheesy gridlines.  Since there aren't line styles, I just
manually dashed the line.  Right now it's hard coded to black - I felt odd
about letting the color be styled, when the fundamental style can't be
changed.