Update to socket2 v0.6 (alexcrichton#614)

Author: Thomasdezeeuw

Cargo.toml

@@ -15,7 +15,7 @@ edition = "2018"
 [dependencies]
 libc = "0.2.42"
 curl-sys = { path = "curl-sys", version = "0.4.77", default-features = false }
-socket2 = "0.5.0"
+socket2 = "0.6.0"
 
 # Unix platforms use OpenSSL for now to provide SSL functionality
 [target.'cfg(all(unix, not(target_os = "macos")))'.dependencies]