Remove the std default feature

Added in 272bb11eaf for reasons that are
unclear to me. It serves no purpose aside from disabling the API of the
entire crate, so it's best to remove it.

Signed-off-by: John Nunley <dev@notgull.net>

Cargo.toml

@@ -17,10 +17,6 @@ exclude = ["/.*"]
 [package.metadata.docs.rs]
 rustdoc-args = ["--cfg", "docsrs"]
 
-[features]
-default = ["std"]
-std = []
-
 [dependencies]
 cfg-if = "1"
 tracing = { version = "0.1.37", default-features = false }

src/lib.rs

@@ -53,8 +53,6 @@
 //! # std::io::Result::Ok(())
 //! ```
 
-#![cfg(feature = "std")]
-#![cfg_attr(not(feature = "std"), no_std)]
 #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
 #![allow(clippy::useless_conversion, clippy::unnecessary_cast, unused_unsafe)]
 #![cfg_attr(docsrs, feature(doc_cfg))]