*  **New Request and Response types,** each with their own builder. There's also
    a `RequestBody` class to write the request body to the network and a
    `ResponseBody` to read the response body from the network. The standalone
    `Headers` class offers full access to the HTTP headers.

 *  **Okio dependency added.** OkHttp now depends on
    [Okio](https://github.com/square/okio), an I/O library that makes it easier