fix argument name for kafka topic

src/main.rs

@@ -28,7 +28,7 @@ fn parse_config() -> ArgMatches<'static> {
         )
         .arg(
             Arg::with_name("topic")
-                .short("k")
+                .short("t")
                 .long("topic")
                 .value_name("NAME")
                 .help("Sets Kafka topic name")