Feature / BC break: Implement PSR-7 http-message interfaces (#54 by @clue)

Replace custom Message, Request, Response and Uri classes with common PSR-7 interfaces:

// old
$browser->get($uri)->then(function (Response $response) {
    echo 'Test: ' . $response->getHeader('X-Test');
    echo 'Body: ' . $response->getBody();
});

// new
$browser->get($uri)->then(function (ResponseInterface $response) {
    if ($response->hasHeader('X-Test')) {
        echo 'Test: ' . $response->getHeaderLine('X-Test');
    }
    echo 'Body: ' . $response->getBody();
});

Feature: Add streaming API (#56 by @clue)

$browser = $browser->withOptions(array('streaming' => true));
$browser->get($uri)->then(function (ResponseInterface $response) {
    $response->getBody()->on('data', function($chunk) {
        echo $chunk . PHP_EOL;
    });
});

Remove / BC break: Remove Browser::resolve() because it's now fully decoupled (#55 by @clue)

If you need this feature, consider explicitly depending on rize/uri-template instead:

$ composer require rize/uri-template

Use clue/block-react and new Promise API in order to simplify tests (#53 by @clue)