TODO

These are mostly ideas, that they're written down here is no guarantee
that they'll ever be done. If you want something done, feel free to
say why or come up with a patch. :-)

support segmented lines
  - put in null value to signify a break in the data set

grid configuration
  - how ticks look like
  - (handling of 1/2 linewidth hack in grid?)

selection
  - user should be able to cancel selection with escape
  - select points

interactive zooming
  - convenience zoom(x1, y1, x2, y2)? and zoomOut() (via zoom stack)?
  - auto-zoom mode?
  - auto-margin

handling time data
  - dataformat
  - axis adjustment
  - tick generation

support for highlighting stuff
  - lines
  - points

legend
  - interactive auto-highlight of graph?

interactive hot points
  - fire event with value

interactive hover over lines
  - fire event with graph id