okhttp 3.4.0 RC1 发布了，更新如下：
改写了 HttpURLConnection 和 HttpsURLConnection.
Cipher suites 现在可能有任意的名称。
CertificatePinner now matches canonicalized hostnames.
Fix: Don’t crash on non-ASCII
ETag headers. Previously OkHttp would reject these headers when validating a cached response.
Fix: Don’t allow remote peer to arbitrarily size the HPACK decoder dynamic table.
Fix: Honor per-host configuration in Android’s network security config. Previously disabling cleartext for any host would disable cleartext for all hosts. Note that this setting is only available on Android 24+.
New: HPACK compression is now dynamic. This should improve performance when transmitting request headers over HTTP/2.
Dispatcher.setIdleCallback() can be used to signal when there are no calls in flight. This is useful for testing with Espresso.
New: Upgrade to Okio 1.9.0.