Fix failure to parse mouserelative event

Cargo.toml

 [package]
 name = "orbclient"
-version = "0.3.26"
+version = "0.3.27"
 authors = ["Jeremy Soller <jackpot51@gmail.com>"]
 description = "The Orbital Client Library"
 documentation = "https://docs.rs/orbclient"

src/event.rs

@@ -71,6 +71,7 @@ impl Event {
             EVENT_NONE => EventOption::None,
             EVENT_KEY => EventOption::Key(KeyEvent::from_event(self)),
             EVENT_MOUSE => EventOption::Mouse(MouseEvent::from_event(self)),
+            EVENT_MOUSE_RELATIVE => EventOption::MouseRelative(MouseRelativeEvent::from_event(self)),
             EVENT_BUTTON => EventOption::Button(ButtonEvent::from_event(self)),
             EVENT_SCROLL => EventOption::Scroll(ScrollEvent::from_event(self)),
             EVENT_QUIT => EventOption::Quit(QuitEvent::from_event(self)),