refactor cpu gauge into standalone widget

widgets/cpu.go

@@ -0,0 +1,26 @@
+package widgets
+
+import (
+	"fmt"
+	"strconv"
+
+	ui "github.com/gizak/termui"
+)
+
+type CPU struct {
+	*ui.Gauge
+}
+
+func NewCPU() *CPU {
+	return &CPU{mkGauge()}
+}
+
+func (c *CPU) Set(val int) {
+	c.BarColor = colorScale(val)
+	c.Label = fmt.Sprintf("%s%%", strconv.Itoa(val))
+	if val < 5 {
+		val = 5
+		c.BarColor = ui.ColorBlack
+	}
+	c.Percent = val
+}