Simplify usage by supporting new default loop

[SimonFrings]

This pull request is a follow up for #32. Thanks to @PaulRotmann for investing time into this 👍.

This changeset simplifies usage by supporting the new default loop.

// old (still supported)
$connector = new ConnectionManagerTimeout($connector, 3.0, $loop);
$delayed = new ConnectionManagerDelayed($connector, 0.5, $loop);

// new (using default loop)
$connector = new ConnectionManagerTimeout($connector, 3.0);
$delayed = new ConnectionManagerDelayed($connector, 0.5);

Builds on top of reactphp/event-loop#226, reactphp/event-loop#229 and reactphp/event-loop#232.

Resolves and Closes #32.

[clue]

@SimonFrings and @PaulRotmann Thanks for the update, changes LGTM!