Fix README Event handler section

[EmmanVazz]

The readme is incorrect.

public void Handle_ValueChanged(object o, int e) should be public void Handle_ValueChanged(object sender, SegmentedControl.FormsPlugin.Abstractions.ValueChangedEventArgs e) as is it in https://github.com/alexrainman/SegmentedControl/blob/master/Demo/SecondPage.xaml.cs#L17 and switch (e) should be switch (e.NewValue) .

It confused me when e was some random int and didn't match the switch case expected values.