servo: assume good defaults for minus and maxus (544 and 2400, as per

the Arduino documentation: http://arduino.cc/en/Reference/ServoAttach)

motion/servo/servo.go

@@ -7,6 +7,11 @@ import (
 	"github.com/kid0m4n/go-rpi/util"
 )
 
+const (
+	minus = 544
+	maxus = 2400
+)
+
 // A PWM interface implements access to a pwm controller.
 type PWM interface {
 	SetMicroseconds(channel int, us int) error
@@ -22,7 +27,7 @@ type Servo struct {
 }
 
 // New creates a new Servo interface.
-func New(pwm PWM, channel int, minus, maxus int) *Servo {
+func New(pwm PWM, channel int) *Servo {
 	return &Servo{
 		PWM:     pwm,
 		Channel: channel,

samples/servo.go

@@ -21,7 +21,7 @@ func main() {
 	pwm.Debug = true
 	defer pwm.Close()
 
-	servo := servo.New(pwm, 0, 500, 2500)
+	servo := servo.New(pwm, 0)
 	servo.Debug = true
 
 	c := make(chan os.Signal, 1)

samples/servoblaster.go

@@ -15,7 +15,7 @@ func main() {
 	sb.Debug = true
 	defer sb.Close()
 
-	servo := servo.New(sb, 0, 500, 2500)
+	servo := servo.New(sb, 0)
 	servo.Debug = true
 
 	c := make(chan os.Signal, 1)