A simple plug in for Flot to draw the axes through the origin when you have data with both negative and positive values.
Note: This plugin will not work with the current stable version of flot (0.7) but should work with any development version after this commit because of the lack of backgroundDraw hooks.
v0.1: Initial version
v0.2: Cleaned up code to remove redundant code. Added border support back. Cleaned up labeling of origin on y-axis when x=0 isn't plotted.