Flesh out plugins event handling, add example stdin plugin (event producer) and echo plugin (event consumer). Next step: fleshing out user/channel structs

src/event/mod.rs

@@ -0,0 +1,8 @@
+use {Channel, User};
+
+#[derive(Debug, Clone)]
+pub enum Event<'a> {
+    Message { sender: &'a User, channel: Option<&'a Channel>, content: String },
+    Join { channel: &'a Channel },
+    Quit { channel: &'a Channel }
+}