Fix grid to not overlap bottom of graph (fixes hiding of line along y-min).
Fix grid to not overlap bottom of graph (fixes hiding of line along y-min).

jessiejea/Flotr2,alanponce/Flotr2,jessiejea/Flotr2,RobertoMalatesta/Flotr2,nicgallardo/Flotr2,nicgallardo/Flotr2,beastlike/Flotr2,alanponce/Flotr2,HumbleSoftware/Flotr2,RobertoMalatesta/Flotr2,jessiejea/Flotr2,beastlike/Flotr2,alanponce/Flotr2,beastlike/Flotr2,HumbleSoftware/Flotr2