Specify autobins = false in Cargo.toml

`cargo build` warns:

    warning: An explicit [[bin]] section is specified in Cargo.toml which
    currently disables Cargo from automatically inferring other binary targets.
    This inference behavior will change in the Rust 2018 edition and the
    following files will be included as a binary target:

    * /Users/kivikakk/Code/Nicoretti/xxd-rs/src/bin/main.rs
    * /Users/kivikakk/Code/Nicoretti/xxd-rs/src/bin/cli.rs

    This is likely to break cargo build or cargo test as these files may not be
    ready to be compiled as a binary target today. You can future-proof yourself
    and disable this warning by adding `autobins = false` to your [package]
    section. You may also move the files to a location where Cargo would not
    automatically infer them to be a target, such as in subfolders.

    For more information on this warning you can consult
    rust-lang/cargo#5330

Cargo.toml

@@ -8,6 +8,7 @@ keywords = ["xxd", "hex-dump"]
 license-file = "LICENSE"
 version = "0.2.3"
 build = "build.rs"
+autobins = false
 
 [badges]
 appveyor = { repository = "Nicoretti/xxd-rs", branch = "master", service = "github" }