Added grid_function routine.
Added grid_function routine.

Added ability to specify data one column at a time to Data.

Improved comments.

Improved demonstration code.


git-svn-id: f83f72cad00039f4d0c1d1188121771302bbc894@37 67c13c2a-ce2d-4362-9fbd-a73952e22801

tschaume/gnuplot-py,tschaume/gnuplot-py