Update installation insctructions

[CedCannes]

Installation instructions needs an update to work with my app using Symfony 2.8.8.
The file M6WebDaemonBundle.php required by my AppKernel is appears only since V 1.2.0.

Installation (that works for me)

Via composer :

"require": {
    "m6web/daemon-bundle":"1.4.*"
}

then enable the bundle in your kernel:

<?php

$bundles = [
    new M6Web\Bundle\DaemonBundle\M6WebDaemonBundle()
];

[Oliver THEBAULT]

I think, this will be fixed with #21 :)

[CedCannes]

Sure, I hadn't seen this PR sorry.