TODO
 ====
  o [MISC] chart.zoom.background needs documenting in each graph types documentation page
  o [PROGRESS] Add "in bar" label (level indicator)
  o [SCATTER] Add chart.ymin
  o [ODO] Look at adding "rivets" decoration
  o [ODO] Add option to not draw the trailing bit on the pointer
  o [SCATTER] Allow specifying the specific point at which the X label is at:
              http://groups.google.com/group/rgraph/browse_thread/thread/5e8debf24acb3e52?hl=en#
 o [BAR] Grouped bar chart and shadows going to the left
 o [SCATTER] Allow stepped lines
 o [THERMOMETER] Add this
 o [ODO] This must always start at zero - this is a bug
 o [MISC] New type of zoom - box
 o [LINE] Mini background for the line
 o [MISC] Add chart.background.grid.autofit to line, bar, and scatter
 o [MISC] Zoom a selection
 o [LINE] Allow multiple shadow colors