Remove needless imports (#159)

src/epoll.rs

@@ -1,6 +1,5 @@
 //! Bindings to epoll (Linux, Android).
 
-use std::convert::TryInto;
 use std::io;
 use std::os::unix::io::{AsFd, AsRawFd, BorrowedFd, RawFd};
 use std::time::Duration;

src/iocp/port.rs

@@ -2,7 +2,6 @@
 
 use super::dur2timeout;
 
-use std::convert::TryInto;
 use std::fmt;
 use std::io;
 use std::marker::PhantomData;

src/poll.rs

@@ -1,7 +1,6 @@
 //! Bindings to poll (VxWorks, Fuchsia, other Unix systems).
 
 use std::collections::HashMap;
-use std::convert::TryInto;
 use std::io;
 use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
 use std::sync::{Condvar, Mutex};