style(all): Run clippy without errors

examples/smtp.rs

@@ -1,30 +0,0 @@
-extern crate lettre;
-
-use lettre::email::EmailBuilder;
-use lettre::transport::EmailTransport;
-use lettre::transport::smtp::SmtpTransportBuilder;
-
-fn main() {
-    let email = EmailBuilder::new()
-        // Addresses can be specified by the tuple (email, alias)
-        .to(("user@example.org", "Firstname Lastname"))
-        // ... or by an address only
-        .from("user@example.com")
-        .subject("Hi, Hello world")
-        .text("Hello world.")
-        .build()
-        .unwrap();
-
-    // Open a local connection on port 25
-    let mut mailer = SmtpTransportBuilder::localhost().unwrap().build();
-    // Send the email
-    let result = mailer.send(email);
-
-    if result.is_ok() {
-        println!("Email sent");
-    } else {
-        println!("Could not send email: {:?}", result);
-    }
-
-    assert!(result.is_ok());
-}