Change default TLS features

Closes #202.

Cargo.toml

@@ -16,7 +16,7 @@ edition = "2018"
 all-features = true
 
 [features]
-default = ["native-tls"]
+default = []
 native-tls = ["native-tls-crate"]
 native-tls-vendored = ["native-tls", "native-tls-crate/vendored"]
 rustls-tls = ["rustls", "webpki", "webpki-roots"]

README.md

@@ -60,7 +60,8 @@ Features
 
 Tungstenite provides a complete implementation of the WebSocket specification.
 TLS is supported on all platforms using native-tls or rustls available through the `native-tls`
-and `rustls-tls` feature flags.
+and `rustls-tls` feature flags. By default **no TLS feature is activated**, so make sure you
+use `native-tls` or `rustls-tls` feature if you need support of the TLS.
 
 There is no support for permessage-deflate at the moment. It's planned.