Failes to request headers from wordpress.org

```Rust
[2020-03-20T12:06:44Z INFO scrape_headers] Visit Headers from 'https://wordpress.org'
[2020-03-20T12:06:44Z DEBUG isahc::agent] agent waker listening on 127.0.0.1:55110
[2020-03-20T12:06:44Z DEBUG isahc::agent] agent took 1.103154ms to start up
[2020-03-20T12:06:44Z INFO surf::middleware::logger::native] sending request
[2020-03-20T12:06:44Z DEBUG isahc::agent] agent ready
[2020-03-20T12:06:44Z DEBUG isahc::handler] initializing handler for request [id=0]
[2020-03-20T12:06:44Z DEBUG isahc::handler] Trying 198.143.164.252:443...
[2020-03-20T12:06:44Z DEBUG isahc::handler] Connected to wordpress.org (198.143.164.252) port 443 (#0)
[2020-03-20T12:06:44Z DEBUG isahc::handler] ALPN, offering h2
[2020-03-20T12:06:44Z DEBUG isahc::handler] ALPN, offering http/1.1
[2020-03-20T12:06:44Z DEBUG isahc::handler] successfully set certificate verify locations:
[2020-03-20T12:06:44Z DEBUG isahc::handler] CAfile: /etc/ssl/certs/ca-certificates.crt
CApath: none
[2020-03-20T12:06:44Z DEBUG isahc::handler] TLSv1.3 (OUT), TLS handshake, Client hello (1):
[2020-03-20T12:06:44Z DEBUG isahc::handler] TLSv1.3 (IN), TLS handshake, Server hello (2):
[2020-03-20T12:06:44Z DEBUG isahc::handler] TLSv1.3 (IN), TLS handshake, Encrypted Extensions (8):
[2020-03-20T12:06:44Z DEBUG isahc::handler] TLSv1.3 (IN), TLS handshake, Certificate (11):
[2020-03-20T12:06:44Z DEBUG isahc::handler] TLSv1.3 (IN), TLS handshake, CERT verify (15):
[2020-03-20T12:06:44Z DEBUG isahc::handler] TLSv1.3 (IN), TLS handshake, Finished (20):
[2020-03-20T12:06:44Z DEBUG isahc::handler] TLSv1.3 (OUT), TLS change cipher, Change cipher spec (1):
[2020-03-20T12:06:44Z DEBUG isahc::handler] TLSv1.3 (OUT), TLS handshake, Finished (20):
[2020-03-20T12:06:44Z DEBUG isahc::handler] SSL connection using TLSv1.3 / TLS_AES_256_GCM_SHA384
[2020-03-20T12:06:44Z DEBUG isahc::handler] ALPN, server accepted to use h2
[2020-03-20T12:06:44Z DEBUG isahc::handler] Server certificate:
[2020-03-20T12:06:44Z DEBUG isahc::handler] subject: OU=Domain Control Validated; CN=*.wordpress.org
[2020-03-20T12:06:44Z DEBUG isahc::handler] start date: Nov 6 17:42:01 2017 GMT
[2020-03-20T12:06:44Z DEBUG isahc::handler] expire date: Dec 15 20:11:21 2020 GMT
[2020-03-20T12:06:44Z DEBUG isahc::handler] subjectAltName: host "wordpress.org" matched cert's "wordpress.org"
[2020-03-20T12:06:44Z DEBUG isahc::handler] issuer: C=US; ST=Arizona; L=Scottsdale; O=GoDaddy.com, Inc.; OU=http://certs.godaddy.com/repository/; CN=Go Daddy Secure Certificate Authority - G2
[2020-03-20T12:06:44Z DEBUG isahc::handler] SSL certificate verify ok.
[2020-03-20T12:06:44Z DEBUG isahc::handler] Using HTTP2, server supports multi-use
[2020-03-20T12:06:44Z DEBUG isahc::handler] Connection state changed (HTTP/2 confirmed)
[2020-03-20T12:06:44Z DEBUG isahc::handler] Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
[2020-03-20T12:06:44Z DEBUG isahc::handler] Using Stream ID: 1 (easy handle 0x55c592198cb0)
[2020-03-20T12:06:44Z DEBUG isahc::handler] TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):
[2020-03-20T12:06:44Z DEBUG isahc::handler] TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):
[2020-03-20T12:06:44Z DEBUG isahc::handler] old SSL session ID is stale, removing
[2020-03-20T12:06:44Z DEBUG isahc::handler] Connection state changed (MAX_CONCURRENT_STREAMS == 128)!
[2020-03-20T12:06:44Z DEBUG isahc::handler] Connection #0 to host wordpress.org left intact
[2020-03-20T12:06:44Z INFO surf::middleware::logger::native] request completed
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: ToStrError { _priv: () }', /home/songtronix/.cargo/registry/src/github.com-1ecc6299db9ec823/surf-2.0.0-alpha.0/src/headers.rs:60:48
stack backtrace:
0: backtrace::backtrace::libunwind::trace
at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/libunwind.rs:86
1: backtrace::backtrace::trace_unsynchronized
at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/mod.rs:66
2: std::sys_common::backtrace::_print_fmt
at src/libstd/sys_common/backtrace.rs:78
3: ::fmt
at src/libstd/sys_common/backtrace.rs:59
4: core::fmt::write
at src/libcore/fmt/mod.rs:1063
5: std::io::Write::write_fmt
at src/libstd/io/mod.rs:1426
6: std::sys_common::backtrace::_print
at src/libstd/sys_common/backtrace.rs:62
7: std::sys_common::backtrace::print
at src/libstd/sys_common/backtrace.rs:49
8: std::panicking::default_hook::{{closure}}
at src/libstd/panicking.rs:204
9: std::panicking::default_hook
at src/libstd/panicking.rs:224
10: std::panicking::rust_panic_with_hook
at src/libstd/panicking.rs:470
11: rust_begin_unwind
at src/libstd/panicking.rs:378
12: core::panicking::panic_fmt
at src/libcore/panicking.rs:111
13: core::option::expect_none_failed
at src/libcore/option.rs:1211
14: ::next
15: as core::future::future::Future>::poll
16: std::thread::local::LocalKey::with
17: std::thread::local::LocalKey::with
18: async_std::task::block_on::block_on
19: scrape_headers::main
20: std::rt::lang_start::{{closure}}
21: std::rt::lang_start_internal::{{closure}}
at src/libstd/rt.rs:52
22: std::panicking::try::do_call
at src/libstd/panicking.rs:303
23: __rust_maybe_catch_panic
at src/libpanic_unwind/lib.rs:86
24: std::panicking::try
at src/libstd/panicking.rs:281
25: std::panic::catch_unwind
at src/libstd/panic.rs:394
26: std::rt::lang_start_internal
at src/libstd/rt.rs:51
27: main
28: __libc_start_main
29: _start
```

Headers returned by https://wordpress.org :
```HTTP
Server: nginx
Date: Fri, 20 Mar 2020 12:05:47 GMT
Content-Type: text/html; charset=utf-8
Connection: keep-alive
Vary: Accept-Encoding
Strict-Transport-Security: max-age=360
X-Olaf: ⛄
X-Frame-Options: SAMEORIGIN
X-nc: HIT ord 1
Content-Encoding: gzip
```

Probably X-Olaf causes issues and to be honest wordpress is the only site which uses it (https://webtechsurvey.com/response-headers/x-olaf/).

Version used: *2.0.0-alpha.0*