Rewrite crate using the native-tls crate

The purpose of this rewrite is to reuse all of awesome logic in the native-tls
crate rather than rewriting it. The native-tls crate already naturally supports
async I/O everywhere so let's just take advantage of it! As a result, this crate
is now stripped of all #[cfg] code essentially and now just provides two
extension traits for `TlsConnector` and `TlsAcceptor`. The extension traits
provide a `connect_async` and `accept_async` function, respectively, which
handles retry logic with mid-handshake streams automatically.

Currently this rewrites drops two current features of this crate: forcing usage
of OpenSSL and a rustls backend. I hope to reenable both of these features
through support in the native-tls crate shortly, however.

.travis.yml

@@ -10,8 +10,6 @@ before_script:
 script:
   - cargo build
   - cargo test
-  - cargo test --features force-openssl
-  - cargo test --features force-rustls
   - cargo doc --no-deps
 after_success:
   - travis-cargo --only nightly doc-upload

Cargo.toml

@@ -13,40 +13,39 @@ for nonblocking I/O streams.
 """
 
 [dependencies]
-cfg-if = "0.1"
-futures = "0.1"
-log = "0.3"
-tokio-core = "0.1"
-
-# Optional dependency that can be enabled with the `force-openssl` feature
-openssl = { version = "0.8", optional = true }
-openssl-verify = { version = "0.2", optional = true }
+futures = "0.1.4"
+tokio-core = "0.1.1"
+native-tls = "0.1"
 
-# Optional dependency to use `rustls` as a backend, enabled with `force-rustls`
-rustls = { version = "0.1.2", optional = true }
-webpki-roots = { version = "0.2", optional = true }
+[dev-dependencies]
+env_logger = { version = "0.3", default-features = false }
+cfg-if = "0.1"
 
-[target.'cfg(all(unix, not(target_os = "macos")))'.dependencies]
-openssl = "0.8"
-openssl-verify = "0.2"
+[target.'cfg(all(not(target_os = "macos"), not(windows)))'.dev-dependencies]
+openssl = "0.9"
 
-[target.'cfg(target_os = "macos")'.dependencies]
+[target.'cfg(target_os = "macos")'.dev-dependencies]
 security-framework = "0.1"
 
-[target.'cfg(windows)'.dependencies]
-schannel = "0.1"
-
 [target.'cfg(windows)'.dev-dependencies]
 advapi32-sys = "0.2"
 crypt32-sys = "0.2"
 kernel32-sys = "0.2"
+schannel = "0.1"
 winapi = "0.2"
 
-[dev-dependencies]
-env_logger = "0.3"
-webpki = "0.3"
-untrusted = "0.3"
+[replace.'native-tls:0.1.0']
+git = 'https://github.com/alexcrichton/rust-native-tls'
+branch = 'changes'
+
+[replace.'security-framework:0.1.9']
+git = 'https://github.com/alexcrichton/rust-security-framework'
+branch = 'handshake2'
+
+[replace.'security-framework-sys:0.1.9']
+git = 'https://github.com/alexcrichton/rust-security-framework'
+branch = 'handshake2'
 
-[features]
-force-openssl = ["openssl", "openssl-verify"]
-force-rustls = ["rustls", "webpki-roots"]
+[replace.'schannel:0.1.1']
+git = 'https://github.com/alexcrichton/schannel-rs'
+branch = 'export-pkcs12'

appveyor.yml

@@ -13,4 +13,3 @@ build: false
 test_script:
   - cargo build
   - cargo test
-  - cargo test --features force-rustls

examples/download-rust-lang.rs

@@ -1,23 +1,28 @@
 extern crate futures;
+extern crate native_tls;
 extern crate tokio_core;
 extern crate tokio_tls;
 
+use std::io;
 use std::net::ToSocketAddrs;
 
 use futures::Future;
-use tokio_core::reactor::Core;
+use native_tls::TlsConnector;
 use tokio_core::net::TcpStream;
-use tokio_tls::ClientContext;
+use tokio_core::reactor::Core;
+use tokio_tls::TlsConnectorExt;
 
 fn main() {
     let mut core = Core::new().unwrap();
     let addr = "www.rust-lang.org:443".to_socket_addrs().unwrap().next().unwrap();
 
     let socket = TcpStream::connect(&addr, &core.handle());
+    let cx = TlsConnector::builder().unwrap().build().unwrap();
 
     let tls_handshake = socket.and_then(|socket| {
-        let cx = ClientContext::new().unwrap();
-        cx.handshake("www.rust-lang.org", socket)
+        cx.connect_async("www.rust-lang.org", socket).map_err(|e| {
+            io::Error::new(io::ErrorKind::Other, e)
+        })
     });
     let request = tls_handshake.and_then(|socket| {
         tokio_core::io::write_all(socket, "\