Update README for 2018 edition

README.md

@@ -22,34 +22,24 @@ To add `elefren` to your project, add the following to the
 elefren = "0.20"
 ```
 
-## Usage
-
-To use this crate in your project, add this to your crate root (lib.rs, main.rs, etc):
-
-```rust,ignore
-extern crate elefren;
-```
-
 ## Example
 
 In your `Cargo.toml`, make sure you enable the `toml` feature:
 
 ```toml
 [dependencies]
-elefren = { version = "0.19", features = ["toml"] }
+elefren = { version = "0.20", features = ["toml"] }
 ```
 
 ```rust,no_run
 // src/main.rs
-extern crate elefren;
-
 use std::error::Error;
 
 use elefren::prelude::*;
 use elefren::helpers::toml; // requires `features = ["toml"]`
 use elefren::helpers::cli;
 
-fn main() -> Result<(), Box<Error>> {
+fn main() -> Result<(), Box<dyn Error>> {
     let mastodon = if let Ok(data) = toml::from_file("mastodon-data.toml") {
         Mastodon::from(data)
     } else {
@@ -63,7 +53,7 @@ fn main() -> Result<(), Box<Error>> {
     Ok(())
 }
 
-fn register() -> Result<Mastodon, Box<Error>> {
+fn register() -> Result<Mastodon, Box<dyn Error>> {
     let registration = Registration::new("https://mastodon.social")
                                     .client_name("elefren-examples")
                                     .build()?;