added error returns to the SendData method on the peripheral interface

peripheral/errors.go

@@ -0,0 +1,9 @@
+package peripheral
+
+import "errors"
+
+var (
+	ErrInvalidData       = errors.New("invalid data")
+	ErrDeviceTimedOut    = errors.New("device timed out")
+	ErrFailureToPackData = errors.New("failed to pack received data")
+)