Update code to 2018 edition

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "httpdate"
-version = "0.3.2"
+version = "1.0.0-alpha"
 authors = ["Pyfisch <pyfisch@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "HTTP date parsing and formatting"
@@ -8,6 +8,7 @@ keywords = ["http", "date", "time", "simple", "timestamp"]
 readme = "README.md"
 documentation = "https://pyfisch.github.io/httpdate/httpdate/index.html"
 repository = "https://github.com/pyfisch/httpdate"
+edition = "2018"
 
 [features]
 unstable = []

src/date.rs

@@ -1,11 +1,9 @@
-#[allow(unused_imports)]
-use std::ascii::AsciiExt;
 use std::fmt::{self, Display, Formatter};
 use std::cmp;
 use std::str::{FromStr, from_utf8_unchecked};
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
-use Error;
+use crate::Error;
 
 /// HTTP timestamp type.
 ///

src/lib.rs

@@ -23,26 +23,19 @@ use std::io;
 use std::num::ParseIntError;
 use std::time::SystemTime;
 
-pub use httpdate::HttpDate;
+pub use date::HttpDate;
 
-mod httpdate;
+mod date;
 
 /// An opaque error type for all parsing errors.
 #[derive(Debug)]
 pub struct Error(());
 
-impl error::Error for Error {
-    fn description(&self) -> &str {
-        "string contains no or an invalid date"
-    }
-    fn cause(&self) -> Option<&error::Error> {
-        None
-    }
-}
+impl error::Error for Error {}
 
 impl Display for Error {
     fn fmt(&self, f: &mut Formatter) -> Result<(), fmt::Error> {
-        f.write_str(error::Error::description(self))
+        f.write_str("string contains no or an invalid date")
     }
 }