Revision history for Perl extension Chart::Plot.

v 0.0 - 08 March 1998 
        first version
v 0.01 - 09 March 1998; 
         - _getOM reports >= max instead of >;
         - fixed bug in setData() data check
v 0.02 - 10 March 1998; 
         - changed error handling in setData() (public method) which
         now returns undef on success and sets $self->error ;
         - changed legend to title (public method)
         - adjusted horizontal tick labels up a bit
v 0.03 - 15 March 1998
         - added colors and dashed line options to dataset graph style
         - added option to pass dataset as two arrays (@xdata, @ydata)
         - added hack for case om == max
v 0.04 - 15 March 1998
         - added general purpose setGraphOptions()
v 0.05 - 18 March 1998
         _ added synopsis to pod
         - added getBounds()
         - Hor axis label is set below and right centered or justified.
         - additional vertical offset if title is present; larger font
v 0.06 - 22 March 1998
         - removed title, offset and axis label methods in favor of
           setGraphOptions()
         - added getBounds()
v 0.07 - 29 May 1998
         - finally put into standard h2xs form
         _ added check for tick step too small
         - changed data validity check to permit scientific notation
           but this invites awful looking tick labels