adding example for stepper motor

examples/raspi_stepper_move.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"fmt"
+
+	"gobot.io/x/gobot"
+	"gobot.io/x/gobot/drivers/gpio"
+	"gobot.io/x/gobot/platforms/raspi"
+)
+
+func main() {
+	r := raspi.NewAdaptor()
+	stepper := gpio.NewStepperDriver(r, [4]string{"7", "11", "13", "15"}, gpio.StepperModes.DualPhaseStepping, 2048)
+
+	work := func() {
+		//set spped
+		stepper.SetSpeed(15)
+
+		//Move forward one revolution
+		if err := stepper.Move(2048); err != nil {
+			fmt.Println(err)
+		}
+
+		//Move backward one revolution
+		if err := stepper.Move(-2048); err != nil {
+			fmt.Println(err)
+		}
+	}
+
+	robot := gobot.NewRobot("stepperBot",
+		[]gobot.Connection{r},
+		[]gobot.Device{stepper},
+		work,
+	)
+
+	robot.Start()
+}