clue/redis-react v2.3.0 on PHP Packagist

Feature: Add new createLazyClient() method to connect only on demand and
implement "idle" timeout to close underlying connection when unused.
(#87 and #88 by @clue and #82 by @WyriHaximus)
```
$client = $factory->createLazyClient('redis://localhost:6379');

$client->incr('hello');
$client->end();
```

Feature: Support cancellation of pending connection attempts.
(#85 by @clue)

$promise = $factory->createClient($redisUri);

$loop->addTimer(3.0, function () use ($promise) {
    $promise->cancel();
});

Feature: Support connection timeouts.
(#86 by @clue)
```
$factory->createClient('localhost?timeout=0.5');
```

Feature: Improve Exception messages for connection issues.
(#89 by @clue)

$factory->createClient('redis://localhost:6379')->then(
    function (Client $client) {
        // client connected (and authenticated)
    },
    function (Exception $e) {
        // an error occurred while trying to connect (or authenticate) client
        echo $e->getMessage() . PHP_EOL;
        if ($e->getPrevious()) {
            echo $e->getPrevious()->getMessage() . PHP_EOL;
        }
    }
);

Improve test suite structure and add forward compatibility with PHPUnit 7 and PHPUnit 6
and test against PHP 7.1, 7.2, and 7.3 on TravisCI.
(#83 by @WyriHaximus and #84 by @clue)
Improve documentation and update project homepage.
(#81 and #90 by @clue)