Vendor dependencies

Let's see how I like this workflow.

vendor/mio/src/event/mod.rs

@@ -0,0 +1,10 @@
+//! Readiness event types and utilities.
+
+#[allow(clippy::module_inception)]
+mod event;
+mod events;
+mod source;
+
+pub use self::event::Event;
+pub use self::events::{Events, Iter};
+pub use self::source::Source;