Support Symfony 7.x and PHP 8.2

#41

For Symfony 5.4 backward compatibility support

Why?

• v7.0.0 drops support for Symfony versions < 6... but some of our applications still require Symfony 4.4/5.4 compatibility

How?

• Use v6.x branch to produce v6.*.* tags for Symfony 4.4/5.4 compatibility

Symfony 6.1 support

To be used only with symfony >=6.1 and php >=8.1

Symfony 5.x support

• drop support for Symfony < 4.4
• add support for Symfony 5.x

PSR-14 implentation for event dispatcher

Merge pull request #32 from M6Web/feat/4.3

feat: psr 14 implentation for event dispatcher

Add SF4 compatibility

Merge pull request #30 from Meroje/patch-1

Make service public for sf4 compatibility

Update Documentation

See #29

Update for PHP7.1, and add >React Event Loop

See #28

Remove support < PHP 7.1

Add eventLoop

Fix travis build

Merge pull request #27 from M6Web/fix/travis-builds

Remove php5.5 build on travis since it's not supported anymore by PHP itself

Remove check on pcntl_signal since it required in composer.json

Merge pull request #25 from lyrixx/my-2-cents

Some cleanup