Update README

Cargo fmt and minor changes

README.md

@@ -20,7 +20,7 @@ modules in Rust.
 
 ### Async
 
-Starting from 0.3, mlua supports async/await for all Lua versions. This feature works using Lua [coroutines](https://www.lua.org/manual/5.3/manual.html#2.6) and require running [Thread](https://docs.rs/mlua/latest/mlua/struct.Thread.html).
+Starting from 0.3, mlua supports async/await for all Lua versions. This works using Lua [coroutines](https://www.lua.org/manual/5.3/manual.html#2.6) and require running [Thread](https://docs.rs/mlua/latest/mlua/struct.Thread.html) along with enabling `async` feature in `Cargo.toml`.
 
 **Examples**:
 - [HTTP Client](examples/async_http_client.rs)

build/main.rs

@@ -81,10 +81,6 @@ fn main() {
     #[cfg(all(feature = "lua51", feature = "luajit"))]
     panic!("You can enable only one of the features: lua53, lua52, lua51, luajit");
 
-    // Async
-    // #[cfg(all(feature = "async", not(any(feature = "lua53", feature = "lua52"))))]
-    // panic!("You can enable async only for: lua53, lua52");
-
     let include_dir = find::probe_lua();
     build_glue(&include_dir);
 }

examples/async_http_client.rs

@@ -2,7 +2,7 @@ use std::collections::HashMap;
 
 use hyper::Client as HyperClient;
 
-use mlua::{Lua, Result, Thread, Error};
+use mlua::{Error, Lua, Result, Thread};
 
 #[tokio::main]
 async fn main() -> Result<()> {
@@ -18,7 +18,10 @@ async fn main() -> Result<()> {
 
         let mut headers = HashMap::new();
         for (key, value) in resp.headers().iter() {
-            headers.entry(key.as_str()).or_insert(Vec::new()).push(value.to_str().unwrap());
+            headers
+                .entry(key.as_str())
+                .or_insert(Vec::new())
+                .push(value.to_str().unwrap());
         }
         lua_resp.set("headers", headers)?;