feature; solving issue #121

There is now a way to allow gaps in charts due to missing
measurements. A style setting (StrokeMaxSpanGap) determines
whether a gap is stroked or not.

An example is included in examples/custom_styles.

examples/custom_styles/main.go

@@ -25,9 +25,10 @@ func main() {
 				Style: chart.Style{
 					StrokeColor: drawing.ColorRed,               // will supercede defaults
 					FillColor:   drawing.ColorRed.WithAlpha(64), // will supercede defaults
+                                        StrokeMaxSpanGap: 2, // do not span gaps more than 2.0 wide
 				},
-				XValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0},
-				YValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0},
+				XValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0, 8.0, 10.0},
+				YValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0, 8.0, 10.0},
 			},
 		},
 	}