Fetching content from HTTPS using rustls (#2024)

* Fetching https

* Fetching dispatcher (HTTP, HTTPS)

* Fetching from github

* Chunked encoding parser

* Abort support

* Fixing tests and review comments

* Cargo.lock order [ci skip]

* Relaxed -> SeqCst

util/https-fetch/examples/fetch.rs

@@ -0,0 +1,15 @@
+extern crate https_fetch;
+
+use std::io;
+use std::sync::Arc;
+use std::sync::atomic::AtomicBool;
+use https_fetch::*;
+
+fn main() {
+	let client = Client::new().unwrap();
+	let aborted = Arc::new(AtomicBool::new(false));
+
+	client.fetch(Url::new("github.com", 443, "/").unwrap(), Box::new(io::stdout()), aborted, |result| {
+		assert!(result.is_ok());
+	}).unwrap();
+}