To do file for Gaston

* add support for map, filledcurves
* add support for colormap
* add support for parametric plots
* add support for curve smoothing
* decide if we'll support ticks
* decide if we need to support more terminals
* add debug options: print gnuplot command line, etc
* look into the mmap interface to avoid creating files
* create script and data files besides plotting -- useful as a starting point
  to further refine the plot using gnuplot directly

ongoing tasks:

* keep improving test frameworks and the tests themselves
* keep improving documentation
